Hi everyone,
I request inclusion of the SAS Transport Layer
and the AIC-94xx SAS LLDD into the Linux kernel.
Please find the latest Linus' git tree with SAS
Transport Layer and AIC-94xx, patches and
a whole tar.bz2 tree here:
http://linux.adaptec.com/sas/
There you will also find the original announcements
posted to this list.
The code is updated twice daily or more often as
needed.
Thank you,
Luben
Luben Tuikov wrote:
> I request inclusion of the SAS Transport Layer
> and the AIC-94xx SAS LLDD into the Linux kernel.
Overall, I see the following major issues. My recommendation is that
this driver live in -mm, or outside the kernel tree, for a while to let
things shake out.
Background
----------
* There is no question that Adaptec's aic94xx and SAS code is correct
WRT the SCSI specifications. The maintainer eats, sleeps, and breathes
SAS specs. :)
* aic94xx hardware supports both SAS and SATA connections. Since SAS
and SATA are intentionally similar electrically, other vendors are
coming out with SATA+SAS hardware too.
* Acronym: "HCIL" Stands for Host/Channel/ID/LUN. Pre-SAS legacy
addressing method.
Issues
------
* Avoids existing SAS code, rather than working with it.
* Avoids existing SATA code, rather than working with it.
* Avoids (rather than fix) several SCSI core false dependencies on HCIL.
Results in code duplication and/or avoidance of needed code.
* So far, it's an Adaptec-only solution. Since it pointedly avoids the
existing SAS transport code, this results in two SAS solutions in Linux:
one for Adaptec, one for {everyone else}.
* Maintainer reminds me of my ATA mentor, Andre Hedrick: knows his
shit, but has difficulties working with the community. May need a
filter if we want long term maintenance to continue.
Resolution
----------
AFAICS, there are two paths:
Easy path: make Adaptec's solution a block driver, which allows it to
sidestep all the "doesn't play well with others" issues. Still an
Adaptec-only solution, but at least its in a separate playpen.
Hard path: Update the SCSI core and libata to work with SATA+SAS
hardware such as Adaptec's.
The hard path takes time, and won't be solved simply by shoving it in.
Jeff
On 09/27/05 17:55, Jeff Garzik wrote:
> * Avoids existing SAS code, rather than working with it.
No, it's the _other_ way around. There is NO existing
SAS code.
My SAS code has been around _long_ before Christophs
code.
Christoph's code is
* MPT based only,
* doesn't follow a spec to save its life,
* far inferior in SAS capabilities and SAS representation
again, due to the fact that it is MPT based.
Since the whole point of MPT is to _hide_ the transport.
> * Avoids existing SATA code, rather than working with it.
FUD! Why? It does _not_ use SATA code at all.
Why? SATA devices are discovered on the domain, but
there is _no_ SATL in the kernel to represent them.
And libata is _not_ SATL. The reasons are that
libata is closely coupled to the hardware, i.e.
ata_port.
While in SAS open transport architecures, you'd have
execute ATA/SAS/SMP task just as you have in aic-94xx.
Why? Because all the chip is, is an interface to the
interconect.
But I'm sure you know all this having looked at the
specs of BCM8603.
> * Avoids (rather than fix) several SCSI core false dependencies on HCIL.
> Results in code duplication and/or avoidance of needed code.
No, not true. It _integrates_ with SCSI Core. The sad truth
is that SCSI Core knows only HCIL.
Jeff, please be more specific.
> * So far, it's an Adaptec-only solution. Since it pointedly avoids the
> existing SAS transport code, this results in two SAS solutions in Linux:
> one for Adaptec, one for {everyone else}.
Hmm, again: _architecture_. And you have to stop these
accusations: "pointedly avoids the existing SAS transport code".
I repeat again that I had this code _long_ before Christoph
ever dreamt up SAS. And he got my code via James B sometime
before OLS this year. I think he got it July 12, 2005.
The question is: why didn't _he_ use the solution already
available?
You have to understand the differences between MPT and open
transport architecture.
At some point I thought Christoph seemed to have understood it.
Now I'm not sure any more.
Now since the open transport solution completely encompasses
and _absolves_ MPT, it is not hard for an MPT driver to
generate a bunch of events and use that infrastructure.
> * Maintainer reminds me of my ATA mentor, Andre Hedrick: knows his
> shit, but has difficulties working with the community. May need a
> filter if we want long term maintenance to continue.
I take offence in your liking me to Andre -- I don't know
Andre personally, but is seems that you're expressing personal
opinion against him, against me and labeling me in some way.
I take offence in that, Jeff.
Why are you making this a _political_ and personal game?
All you're doing is trying to aliken me to someone and
brandish me as someone I'm not.
This is rude, offensive and done in desperation.
Shall we concentrate on the _technical_ part of
the argument?
I repeat again: _technical_ part of the argument.
> Easy path: make Adaptec's solution a block driver, which allows it to
> sidestep all the "doesn't play well with others" issues. Still an
What _exactly_ does it mean "don't play well with others"?
Do you mean:
- the solution is far superiour to anything available now
- it presents the SAS Domain in sysfs as it looks in
the physical world,
- does domain discovery and expander configuration,
- allows for complete control of the domain to user space,
- it pokes at SCSI Core's 20 year old relics.
- it's a thorn in the flesh to other people striving for
similar functionality.
Or do you mean:
- it does not change a single line of code in the kernel,
- does not break anything existing,
- etc, etc.
> Adaptec-only solution, but at least its in a separate playpen.
I'm sure James Bottomley will move from SCSI Core to the block
layer as he did for IDR. hehehe :-)
And no, it is not Adaptec's only solution. Your BCM8603 SAS
LLDD when you write it could use it without any problems.
> Hard path: Update the SCSI core and libata to work with SATA+SAS
> hardware such as Adaptec's.
Cannot do for libata -- ever. Why? You know best: because
libata uses direct access to the hardware! There is no
layered architecture.
What you need to do is to write a SATL layer, just as you can
see in SAT-r6, page 2, Figure 3. I'm on top of this already.
But in order to do this you need a unified architecture
for accessing ATA devices.
Now libata, uses ata_port to do this, which is _hardware_
access.
The SAS Transport layer uses Execute SCSI RPC (defined
in SAM, provided by aic94xx) to do this.
So in effect, what SATL would end up to be is a
data transformation function. But I digress...
> The hard path takes time, and won't be solved simply by shoving it in.
No, you can do it now. It will not affect anyone or anything.
(Other than hurting a couple of people's pride.)
The code doesn't alter Linux SCSI or anyone else's behaviour.
It only _provides_ SAS support to the kernel.
Including it in as is would does not hurt anyone as you can
see here:
http://linux.adaptec.com/sas/git/
Concentrate on the _technical_ merit, let's be more specific.
Luben
Luben,
Welcome to the club ...
You have managed to prove your knowledge base and forgot everything
learned in kindergarden. Since I have kids, and spent time back in
kindergarden, there are some valuable lessons there many have forgotten.
>From what I have seen here, both sides have some valid points.
>From what I know from history and why I no longer maintain anything,
(working to get sanity back) is the Maintainer defines direction while
following a bigger picture.
The issues wrt to HCIL v/s WWN v/s Multiplier v/s Target-Mode v/s blahblah
blahblah are important questions.
Remember, everything about storage is a lie.
Help create a better lie by mapping into the design set forward by James
and company. If the goal of Adaptec is to have support then they need to
buckup and play be to rules at hand. Remember, most people are open to
new ideas and better models. Propose one and you will find backing.
Since you are in the bay-area ... want to met who you have been associated
with ... or is the idea to weird?
Cheers,
Andre
On Tue, 27 Sep 2005, Luben Tuikov wrote:
> On 09/27/05 17:55, Jeff Garzik wrote:
> > * Avoids existing SAS code, rather than working with it.
>
> No, it's the _other_ way around. There is NO existing
> SAS code.
>
> My SAS code has been around _long_ before Christophs
> code.
>
> Christoph's code is
> * MPT based only,
> * doesn't follow a spec to save its life,
> * far inferior in SAS capabilities and SAS representation
> again, due to the fact that it is MPT based.
>
> Since the whole point of MPT is to _hide_ the transport.
>
> > * Avoids existing SATA code, rather than working with it.
>
> FUD! Why? It does _not_ use SATA code at all.
>
> Why? SATA devices are discovered on the domain, but
> there is _no_ SATL in the kernel to represent them.
>
> And libata is _not_ SATL. The reasons are that
> libata is closely coupled to the hardware, i.e.
> ata_port.
>
> While in SAS open transport architecures, you'd have
> execute ATA/SAS/SMP task just as you have in aic-94xx.
> Why? Because all the chip is, is an interface to the
> interconect.
>
> But I'm sure you know all this having looked at the
> specs of BCM8603.
>
> > * Avoids (rather than fix) several SCSI core false dependencies on HCIL.
> > Results in code duplication and/or avoidance of needed code.
>
> No, not true. It _integrates_ with SCSI Core. The sad truth
> is that SCSI Core knows only HCIL.
>
> Jeff, please be more specific.
>
> > * So far, it's an Adaptec-only solution. Since it pointedly avoids the
> > existing SAS transport code, this results in two SAS solutions in Linux:
> > one for Adaptec, one for {everyone else}.
>
> Hmm, again: _architecture_. And you have to stop these
> accusations: "pointedly avoids the existing SAS transport code".
>
> I repeat again that I had this code _long_ before Christoph
> ever dreamt up SAS. And he got my code via James B sometime
> before OLS this year. I think he got it July 12, 2005.
>
> The question is: why didn't _he_ use the solution already
> available?
>
> You have to understand the differences between MPT and open
> transport architecture.
>
> At some point I thought Christoph seemed to have understood it.
> Now I'm not sure any more.
>
> Now since the open transport solution completely encompasses
> and _absolves_ MPT, it is not hard for an MPT driver to
> generate a bunch of events and use that infrastructure.
>
> > * Maintainer reminds me of my ATA mentor, Andre Hedrick: knows his
> > shit, but has difficulties working with the community. May need a
> > filter if we want long term maintenance to continue.
>
> I take offence in your liking me to Andre -- I don't know
> Andre personally, but is seems that you're expressing personal
> opinion against him, against me and labeling me in some way.
>
> I take offence in that, Jeff.
>
> Why are you making this a _political_ and personal game?
>
> All you're doing is trying to aliken me to someone and
> brandish me as someone I'm not.
>
> This is rude, offensive and done in desperation.
>
> Shall we concentrate on the _technical_ part of
> the argument?
>
> I repeat again: _technical_ part of the argument.
>
> > Easy path: make Adaptec's solution a block driver, which allows it to
> > sidestep all the "doesn't play well with others" issues. Still an
>
> What _exactly_ does it mean "don't play well with others"?
>
> Do you mean:
> - the solution is far superiour to anything available now
> - it presents the SAS Domain in sysfs as it looks in
> the physical world,
> - does domain discovery and expander configuration,
> - allows for complete control of the domain to user space,
> - it pokes at SCSI Core's 20 year old relics.
> - it's a thorn in the flesh to other people striving for
> similar functionality.
>
> Or do you mean:
> - it does not change a single line of code in the kernel,
> - does not break anything existing,
> - etc, etc.
>
> > Adaptec-only solution, but at least its in a separate playpen.
>
> I'm sure James Bottomley will move from SCSI Core to the block
> layer as he did for IDR. hehehe :-)
>
> And no, it is not Adaptec's only solution. Your BCM8603 SAS
> LLDD when you write it could use it without any problems.
>
> > Hard path: Update the SCSI core and libata to work with SATA+SAS
> > hardware such as Adaptec's.
>
> Cannot do for libata -- ever. Why? You know best: because
> libata uses direct access to the hardware! There is no
> layered architecture.
>
> What you need to do is to write a SATL layer, just as you can
> see in SAT-r6, page 2, Figure 3. I'm on top of this already.
>
> But in order to do this you need a unified architecture
> for accessing ATA devices.
>
> Now libata, uses ata_port to do this, which is _hardware_
> access.
>
> The SAS Transport layer uses Execute SCSI RPC (defined
> in SAM, provided by aic94xx) to do this.
>
> So in effect, what SATL would end up to be is a
> data transformation function. But I digress...
>
> > The hard path takes time, and won't be solved simply by shoving it in.
>
> No, you can do it now. It will not affect anyone or anything.
> (Other than hurting a couple of people's pride.)
>
> The code doesn't alter Linux SCSI or anyone else's behaviour.
> It only _provides_ SAS support to the kernel.
>
> Including it in as is would does not hurt anyone as you can
> see here:
> http://linux.adaptec.com/sas/git/
>
> Concentrate on the _technical_ merit, let's be more specific.
>
> Luben
>
> -
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> Please read the FAQ at http://www.tux.org/lkml/
>
Luben Tuikov wrote:
> On 09/27/05 17:55, Jeff Garzik wrote:
>
>>* Avoids existing SAS code, rather than working with it.
> No, it's the _other_ way around. There is NO existing
> SAS code.
Incorrect, just look in the latest upstream kernel.
>>* Avoids existing SATA code, rather than working with it.
>
>
> FUD! Why? It does _not_ use SATA code at all.
That's the problem.
> Why? SATA devices are discovered on the domain, but
> there is _no_ SATL in the kernel to represent them.
>
> And libata is _not_ SATL. The reasons are that
libata-scsi.c is the SAT translation layer.
>>* Avoids (rather than fix) several SCSI core false dependencies on HCIL.
>> Results in code duplication and/or avoidance of needed code.
>
>
> No, not true. It _integrates_ with SCSI Core. The sad truth
> is that SCSI Core knows only HCIL.
That's something that needs fixing, for SAS.
> I repeat again that I had this code _long_ before Christoph
> ever dreamt up SAS. And he got my code via James B sometime
> before OLS this year. I think he got it July 12, 2005.
>
> The question is: why didn't _he_ use the solution already
> available?
Because it has the problems listed time and again.
> You have to understand the differences between MPT and open
> transport architecture.
>
> At some point I thought Christoph seemed to have understood it.
> Now I'm not sure any more.
>
> Now since the open transport solution completely encompasses
> and _absolves_ MPT, it is not hard for an MPT driver to
> generate a bunch of events and use that infrastructure.
The SAS transport class is designed to support both firmware-based
devices like MPT, and non-firmware devices such as Adaptec.
Sure it might need patches -- send patches, work with people, rather
than ignoring existing work.
>>* Maintainer reminds me of my ATA mentor, Andre Hedrick: knows his
>>shit, but has difficulties working with the community. May need a
>>filter if we want long term maintenance to continue.
>
>
> I take offence in your liking me to Andre -- I don't know
> Andre personally, but is seems that you're expressing personal
> opinion against him, against me and labeling me in some way.
>
> I take offence in that, Jeff.
>
> Why are you making this a _political_ and personal game?
>
> All you're doing is trying to aliken me to someone and
> brandish me as someone I'm not.
>
> This is rude, offensive and done in desperation.
>
> Shall we concentrate on the _technical_ part of
> the argument?
>
> I repeat again: _technical_ part of the argument.
We've been over the technical stuff time and again. That's the
maintainer problem. We need someone who will listen to the community.
>>Easy path: make Adaptec's solution a block driver, which allows it to
>>sidestep all the "doesn't play well with others" issues. Still an
>
>
> What _exactly_ does it mean "don't play well with others"?
It means not taking feedback, and working around rather than with the
SCSI core.
>>Adaptec-only solution, but at least its in a separate playpen.
>
>
> I'm sure James Bottomley will move from SCSI Core to the block
> layer as he did for IDR. hehehe :-)
>
> And no, it is not Adaptec's only solution. Your BCM8603 SAS
> LLDD when you write it could use it without any problems.
>
>
>>Hard path: Update the SCSI core and libata to work with SATA+SAS
>>hardware such as Adaptec's.
>
>
> Cannot do for libata -- ever. Why? You know best: because
> libata uses direct access to the hardware! There is no
> layered architecture.
Then you don't understand the ->qc_{prep,issue} hooks. That should get
you 90% of the way there, if not 99%.
> What you need to do is to write a SATL layer, just as you can
> see in SAT-r6, page 2, Figure 3. I'm on top of this already.
Re-read libata-scsi.c, and submit any patches you feel are needed.
> The code doesn't alter Linux SCSI or anyone else's behaviour.
> It only _provides_ SAS support to the kernel.
That's one of the problems: It should update the SCSI core.
Jeff
Hi Andre,
--- Andre Hedrick <[email protected]> wrote:
> From what I know from history and why I no longer maintain anything,
> (working to get sanity back) is the Maintainer defines direction while
> following a bigger picture.
Yes, and I think you'll agree with me, the Maintainer isn't/shouldn't
necessarily be the person "defining direction". The reasons are
many but mostly:
* Documentation/ManagingStyle document (valuable read),
That document _really_ says it _all_. I suggest all developers, maintainers,
and corporate _management_ reading this thread to read it.
Why should the Maintainer be "defining direction"? Is this some
religous cult where "Beaver knows best?" (punt intended!)
Or is this a theocratic society here at Linux SCSI? "Pi = 3" ;-)
The maintainership role is and has been _clearly_ defined! For the
sake of eveyone else, take a look at 2.4 maintainer, 2.6 maintainer,
other subsystem maintainers: defined by example and in word.
So much unlike SCSI Core.
Another also great reason is:
* Complete, utter and infinite _incompetence_ coupled with too much pride.
It hurts us all.
When it comes down to it SCSI Core is 20 years behind and thus Linux Storage
is 20 years behind.
> Help create a better lie by mapping into the design set forward by James
> and company. If the goal of Adaptec is to have support then they need to
Yes, this is indeed a very valuable advice. I hadn't ever looked at it
like that.
What I thought, albeit erroneously, mea culpa, is that Linux actually
_wanted_ to be "the storage OS of choice". Now I see and realize that
due to neglected management, Linux has very little to do with _storage_.
Linux need to thank the mutitude of storage ignorant customers
willing to pay the buck, because it is _Linux_ (put gasping sound here).
Linux _can_ be the "storage OS of choice", but this will not happen
through neglect, or sheer incompetence coupled with lots of pride.
Back on topic: I'll try to keep up this "Linux storage lie" set forth
by the james-bottomleys of the Linux community.
> buckup and play be to rules at hand. Remember, most people are open to
> new ideas and better models. Propose one and you will find backing.
I never have found backing. It is all in the archives of linux-scsi
mailing list. What happens is that even if people like your idea
and write to you _privately_ to tell you that they like your
idea, somewhere in their email, they tell you not to cross-post
their message to the list because they have storage products which
need Linux. The reason for this is that James Bottomley has established
this politics that if you don't agree to his antics, your patches are
never ever going in. Why else do you think IBM-ers agree with him that
Linux SCSI doesn't need 64 bit LUNS?
_But_ I'm willing to try _again_. So I'll be proposing something
later this morning. (You know, all engineers are optimists.)
Luben
On Wed, Sep 28, 2005 at 04:37:03AM -0700, Luben Tuikov wrote:
> Yes, and I think you'll agree with me, the Maintainer isn't/shouldn't
> necessarily be the person "defining direction". The reasons are
> many but mostly:
> * Documentation/ManagingStyle document (valuable read),
> That document _really_ says it _all_. I suggest all developers, maintainers,
> and corporate _management_ reading this thread to read it.
Dude, that document is written in a very tongue-in-cheek style. There's
a few clues:
"the preferred (or made up, depending on who you ask) management style"
"this document may or may not have anything to do with reality. It
started as a lark"
It's really not a club for you to beat James with.
On Wed, 28 Sep 2005, Matthew Wilcox wrote:
>
> Dude, that document is written in a very tongue-in-cheek style.
True, true. But sometimes you can say painful truths more easily if you do
it as a joke. Most of the ManagementStyle document is perfectly valid.
Whether it has any bearing on this discussion is another matter ;)
Linus
On Wed, Sep 28, 2005 at 04:37:03AM -0700, Luben Tuikov wrote:
> never ever going in. Why else do you think IBM-ers agree with him that
> Linux SCSI doesn't need 64 bit LUNS?
Please stop repeating that, no one said we should *not* implement a 64 bit
LUN in linux scsi, and James posted a patch for 64 bit LUN. I posted a
clarification in response to your earlier postings, you seem to have
ignored or forgotten this post:
http://marc.theaimsgroup.com/?l=linux-scsi&m=112671847228275&w=2
I said:
"I am talking about the scsi spec, not the code. IMO linux scsi code
should support W_LUN and 64 bit LUN."
-- Patrick Mansfield
On Wed, 28 Sep 2005 04:37:03 PDT, Luben Tuikov said:
> When it comes down to it SCSI Core is 20 years behind and thus Linux Storage
> is 20 years behind.
Hmm.. 20 years ago I was hooking Fujitsu Super-Eagles to Sun3/280 servers.
If you're going to claim that the current SCSI core is *that* far behind, you're
going to have to back it up. Remember that making exaggerated claims is a good
way to make people not listen to the *rest* of your message.
Seen in include/scsi/scsi.h:
/*
* FIXME: bit0 is listed as reserved in SCSI-2, but is
* significant in SCSI-3. For now, we follow the SCSI-2
* behaviour and ignore reserved bits.
*/
So obviously, it's at least the number of years since SCSI-3 was defined,
but no more than the time since SCSI-2. According to http://home.comcast.net/~SCSIguy/SCSI_FAQ/scsifaq.html
SCSI-2 devices started showing up in 1988, and X3.131-1994 came out in 1994.
1996 saw the first SCSI-3 proposals.
I'll give you *one* decade, but not two. :)
On 09/28/05 12:27, Patrick Mansfield wrote:
> On Wed, Sep 28, 2005 at 04:37:03AM -0700, Luben Tuikov wrote:
>
>
>>never ever going in. Why else do you think IBM-ers agree with him that
>>Linux SCSI doesn't need 64 bit LUNS?
>
>
> Please stop repeating that, no one said we should *not* implement a 64 bit
> LUN in linux scsi, and James posted a patch for 64 bit LUN. I posted a
> clarification in response to your earlier postings, you seem to have
> ignored or forgotten this post:
>
> http://marc.theaimsgroup.com/?l=linux-scsi&m=112671847228275&w=2
Sorry.
I was refering to the bottom of this email:
http://marc.theaimsgroup.com/?l=linux-scsi&m=112665156918643&w=2
Luben
On 09/28/05 12:30, [email protected] wrote:
> On Wed, 28 Sep 2005 04:37:03 PDT, Luben Tuikov said:
>
>
>>When it comes down to it SCSI Core is 20 years behind and thus Linux Storage
>>is 20 years behind.
>
>
> Hmm.. 20 years ago I was hooking Fujitsu Super-Eagles to Sun3/280 servers.
> If you're going to claim that the current SCSI core is *that* far behind, you're
> going to have to back it up. Remember that making exaggerated claims is a good
> way to make people not listen to the *rest* of your message.
>
> Seen in include/scsi/scsi.h:
>
> /*
> * FIXME: bit0 is listed as reserved in SCSI-2, but is
> * significant in SCSI-3. For now, we follow the SCSI-2
> * behaviour and ignore reserved bits.
> */
>
> So obviously, it's at least the number of years since SCSI-3 was defined,
> but no more than the time since SCSI-2. According to http://home.comcast.net/~SCSIguy/SCSI_FAQ/scsifaq.html
> SCSI-2 devices started showing up in 1988, and X3.131-1994 came out in 1994.
> 1996 saw the first SCSI-3 proposals.
>
> I'll give you *one* decade, but not two. :)
Ok, I'll take that.
BTW, I was referring to the _architecture_ of SCSI Core.
It hasn't seen any _innovation_ for the last 5 years
as far as SCSI or Storage is concerned.
Luben
Hi Patrick,
You have hit on one of the key word of my downfall.
Specifications!!!
I believe in them and they are the inflexable state machine which all OSes
are required to address. Linux has a very bad history of avoiding the
boundary conditions related to storage.
I am for following the rules of the spec, and will bet Linus would now
agree more so than before. The problem is SCSI is a strange beast without
a formal FSM. It is more of a BusPhase psuedo stated transport. It is
smart enough to laugh at bad software designs and keep going. Sheesh,
look at M$'s miniport.
This leads me to a point where a similar (but smarter) miniport could look
interesting. However, this is also where the transport classes have their
bases, afaics. Anyone please correct me where I have mistated (other than
Linus, :-p).
Luben, I have a vested interest in seeing SAS run via SCSI. So this means
you have one ex-demi-god from the world of maintainers looking to pull you
have towards the current path and open to ideas and willing to back a
better design and push it.
Cheers,
Andre Hedrick
LAD Storage Consulting Group
On Wed, 28 Sep 2005, Patrick Mansfield wrote:
> On Wed, Sep 28, 2005 at 04:37:03AM -0700, Luben Tuikov wrote:
>
> > never ever going in. Why else do you think IBM-ers agree with him that
> > Linux SCSI doesn't need 64 bit LUNS?
>
> Please stop repeating that, no one said we should *not* implement a 64 bit
> LUN in linux scsi, and James posted a patch for 64 bit LUN. I posted a
> clarification in response to your earlier postings, you seem to have
> ignored or forgotten this post:
>
> http://marc.theaimsgroup.com/?l=linux-scsi&m=112671847228275&w=2
>
> I said:
>
> "I am talking about the scsi spec, not the code. IMO linux scsi code
> should support W_LUN and 64 bit LUN."
>
> -- Patrick Mansfield
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
On 09/27/05 22:02, Jeff Garzik wrote:
> Luben Tuikov wrote:
>
>>On 09/27/05 17:55, Jeff Garzik wrote:
>>
>>
>>>* Avoids existing SAS code, rather than working with it.
>
>
>>No, it's the _other_ way around. There is NO existing
>>SAS code.
>
>
> Incorrect, just look in the latest upstream kernel.
Yes, because it was Christoph's code submitted right after
I submitted and JB took his code right in.
Again, I had the infrastructure ready _before_ OLS.
> libata-scsi.c is the SAT translation layer.
Not quite.
It has potential to become SATL but at its current
form it cannot be:
int ata_scsi_queuecmd(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *))
{
struct ata_port *ap;
struct ata_device *dev;
struct scsi_device *scsidev = cmd->device;
ap = (struct ata_port *) &scsidev->host->hostdata[0];
If I want to use that I have to _simulate_ ata_port.
Furthermore, scsidev->host->hostdata may not point
to ata_port for SATA devices over a different transport.
Ideally SATL is just a _data transformation function_ and
getting to the ATA device is transport dependent.
Jeff, would you be accepting patches?
>>No, not true. It _integrates_ with SCSI Core. The sad truth
>>is that SCSI Core knows only HCIL.
>
>
> That's something that needs fixing, for SAS.
Would you be accepting patches for the creation,
and use of "struct scsi_domain_device { ... }"?
This would be a "SCSI Device with a Z Port".
Z could be target or initiator (most likely just T).
Then for each scsi_domain_device, SCSI Core does
REPORT LUNS and then INQUIRY for each LU it found.
The old (current) code would still say as is, unchanged,
since it supports older, broken hardware.
Would you be accepting patches for this?
>>I repeat again that I had this code _long_ before Christoph
>>ever dreamt up SAS. And he got my code via James B sometime
>>before OLS this year. I think he got it July 12, 2005.
>>
>>The question is: why didn't _he_ use the solution already
>>available?
>
>
> Because it has the problems listed time and again.
What problems when there was no other code around.
Look at it this way: _their_ code doesn't integrate
with ours. See?
I simply cannot take an argument like this:
"Because it has the problems listed time and again."
You have to be specific.
> The SAS transport class is designed to support both firmware-based
> devices like MPT, and non-firmware devices such as Adaptec.
No, it never has been. It is an _attribute_ exporting framework
only.
If you understood how different those architectures are,
you'd understand what I mean.
> Sure it might need patches -- send patches, work with people, rather
> than ignoring existing work.
I do not _know_ how to consolidate the completely broken
"design" set forth by JB and company.
It is _completely_ not to SAM spec.
Exporting attributes from MPT-based drivers is not the same
as managing a transport.
I repeat again:
* MPT _hides_ the transport and the managment
of the transport from you -- so in effect there is
nothing to manage.
* MPT gives you Logical Units to work with, NOT ever domain
devices or anyhing domain like.
* MPT gives you a SAM/SPC hook to hook _right_ into SCSI Core.
_This_ is why their LLDD _can_ use the host template.
But an AIC-94xx and BCM8603 _is_ NOT a scsi_host material. It is just
an interface to the interconnect.
To convince yourself of this: take a look at the _members_ of
the scsi host/scsi host template: nothing in that structure is
presented in the chip -- UNLIKE old Parallel SCSI device drivers.
The scsi host template was written to cater to _old_ (then new)
Parallel SCSI drivers! Times have changed! Time to evolve.
> We've been over the technical stuff time and again. That's the
> maintainer problem.
No we haven't been over the technical stuff time and again.
> We need someone who will listen to the community.
I bet you're melting people's hearts when they read this.
So to summarize for corporate management what you're saying
here is:
- you're saying that I do not listen to "the community",
- you're saying that I'm an _outsider_ to "the community",
- you're saying that I'm no good to work with you, since
you are part of that community but not me.
That is you cannot take it that someone will tell
"the community" anything. "The community" knows all and it
knows best.
So in effect there are no good and knowlegable engineers
anywhere but in the "Linux community".
That is there is no people with new ideas, better ideas,
innovative ideas, more knowlege about certain subject matter,
_anywhere_ but in the "Linux community".
So in effect, there will never be an "outsider" who will
come in to the "linux community" and change things around,
no fresh ideas, no better (right?) way to do things.
"The community" is not going to listen to anyone but only to
already politically established members on _any_ subject
matter, even technical, even from "outsiders" who work with
the technology every day.
>>What _exactly_ does it mean "don't play well with others"?
>
>
> It means not taking feedback, and working around rather than with the
> SCSI core.
So does this mean, that if I submit patches "fixing" (oops,
not meant to hurt anyone's bal^w^w^wpride) SCSI Core, they
will be accepted.
Or do you want me to do "your way of SAS"?
Maybe JB et al, should write the "Linux SAS spec" and
then we can recommend this to T10.org, so they can scrap
their version and use "the community's"?
I hear there was such a suggestion on the mailing lists
for ATA and T13.org, but I'm sure I'm misunderstanding
something here as usual.
> Then you don't understand the ->qc_{prep,issue} hooks. That should get
> you 90% of the way there, if not 99%.
But I have to simulate struct ata_port, Jeff.
Which isn't so bad, but speaks about the design.
>>What you need to do is to write a SATL layer, just as you can
>>see in SAT-r6, page 2, Figure 3. I'm on top of this already.
>
> Re-read libata-scsi.c, and submit any patches you feel are needed.
Will do.
>>The code doesn't alter Linux SCSI or anyone else's behaviour.
>>It only _provides_ SAS support to the kernel.
>
>
> That's one of the problems: It should update the SCSI core.
Thank you for admitting this -- you're the first and only
member of "the community" (since I'm not a member apparently)
to admit this.
Luben
On 09/28/05 15:45, Andre Hedrick wrote:
> Hi Patrick,
>
> You have hit on one of the key word of my downfall.
>
> Specifications!!!
>
> I believe in them and they are the inflexable state machine which all OSes
> are required to address.
Me too. I live and breathe by them.
> I am for following the rules of the spec, and will bet Linus would now
> agree more so than before.
Me too.
An interesting thing which "the community" would appreciate is
that M$ has aggressively started to "go by the spec" as far
as SCSI is concerned.
Ding-ding!
> The problem is SCSI is a strange beast without
> a formal FSM. It is more of a BusPhase psuedo stated transport. It is
Oh, no, no, no! So much has changed Andre.
Just take a look at SAM, and I'm sure that you'll appreciate the object
oriented design, the abstractions, etc. Really!
Recently all new protocols follow _explicit_ state machine definitions
at each layer they define, and how it interacts with the layer
above and below again by FSMs. It's all a good thing.
> Luben, I have a vested interest in seeing SAS run via SCSI. So this means
> you have one ex-demi-god from the world of maintainers looking to pull you
> have towards the current path and open to ideas and willing to back a
> better design and push it.
Ok, thanks Andre. Much appreciated.
You are the first person to back me up _publicly_. Now if we
can find a person from "the community" to do that, and get all
the other people who've written me _privately_, we'd be in
good shape.
Luben
P.S. Not sure if you have seen this link:
http://linux.adaptec.com/sas/
Luben Tuikov wrote:
> Ideally SATL is just a _data transformation function_ and
> getting to the ATA device is transport dependent.
Incorrect. It needs to issue multiple ATA commands to emulate a single
SCSI command, cache some state, and other details. Not purely data
transformation.
> Jeff, would you be accepting patches?
Yes. That's what I mean when I say "submit patches".
>>>No, not true. It _integrates_ with SCSI Core. The sad truth
>>>is that SCSI Core knows only HCIL.
>>
>>
>>That's something that needs fixing, for SAS.
>
>
> Would you be accepting patches for the creation,
> and use of "struct scsi_domain_device { ... }"?
>
> This would be a "SCSI Device with a Z Port".
> Z could be target or initiator (most likely just T).
>
> Then for each scsi_domain_device, SCSI Core does
> REPORT LUNS and then INQUIRY for each LU it found.
>
> The old (current) code would still say as is, unchanged,
> since it supports older, broken hardware.
>
> Would you be accepting patches for this?
What needs to happen is that SPI-specific stuff in the SCSI core needs
to be moved to SPI-specific transport code.
Then all transports will be at an equal level, and the SCSI core will be
fully transport-agnostic.
>>>I repeat again that I had this code _long_ before Christoph
>>>ever dreamt up SAS. And he got my code via James B sometime
>>>before OLS this year. I think he got it July 12, 2005.
>>>
>>>The question is: why didn't _he_ use the solution already
>>>available?
>>
>>
>>Because it has the problems listed time and again.
>
>
> What problems when there was no other code around.
>
> Look at it this way: _their_ code doesn't integrate
> with ours. See?
>
> I simply cannot take an argument like this:
> "Because it has the problems listed time and again."
>
> You have to be specific.
"time and again" means that we have been specific multiple times.
Re-read your emails from James and Christoph :)
>>The SAS transport class is designed to support both firmware-based
>>devices like MPT, and non-firmware devices such as Adaptec.
>
>
> No, it never has been. It is an _attribute_ exporting framework
> only.
>
> If you understood how different those architectures are,
> you'd understand what I mean.
James is wrong here. The "transport class" in reality winds up as a
transport lib, in addition to simply exporting attributes.
There will always be functions that are common to a transport.
Christoph calls this "libsas", since software-driven SAS implementations
will share this transport code, but not necessarily all SAS
implementations (MPT, qla etc.).
>>Sure it might need patches -- send patches, work with people, rather
>>than ignoring existing work.
>
>
> I do not _know_ how to consolidate the completely broken
> "design" set forth by JB and company.
>
> It is _completely_ not to SAM spec.
Not true. Just because SCSI core lacks an explicit "execute SCSI
command" RPC hook, does not imply that that capability is non-existent.
Stare at the Scsi_Host_Template some more and you'll see it.
> Exporting attributes from MPT-based drivers is not the same
> as managing a transport.
>
> I repeat again:
> * MPT _hides_ the transport and the managment
> of the transport from you -- so in effect there is
> nothing to manage.
> * MPT gives you Logical Units to work with, NOT ever domain
> devices or anyhing domain like.
> * MPT gives you a SAM/SPC hook to hook _right_ into SCSI Core.
>
> _This_ is why their LLDD _can_ use the host template.
>
> But an AIC-94xx and BCM8603 _is_ NOT a scsi_host material. It is just
> an interface to the interconnect.
A scsi_host is simply a container. You're being too literal.
> To convince yourself of this: take a look at the _members_ of
> the scsi host/scsi host template: nothing in that structure is
> presented in the chip -- UNLIKE old Parallel SCSI device drivers.
>
> The scsi host template was written to cater to _old_ (then new)
> Parallel SCSI drivers! Times have changed! Time to evolve.
Yes. We need to evolve the SCSI core to separate out SPI-specific
pieces, to make it more transport-agnostic.
>>We've been over the technical stuff time and again. That's the
>> maintainer problem.
>
>
> No we haven't been over the technical stuff time and again.
>
>
>>We need someone who will listen to the community.
>
>
> I bet you're melting people's hearts when they read this.
>
> So to summarize for corporate management what you're saying
> here is:
> - you're saying that I do not listen to "the community",
correct
> - you're saying that I'm an _outsider_ to "the community",
irrelevant
> - you're saying that I'm no good to work with you, since
> you are part of that community but not me.
irrelevant
> That is you cannot take it that someone will tell
> "the community" anything. "The community" knows all and it
> knows best.
>
> So in effect there are no good and knowlegable engineers
> anywhere but in the "Linux community".
>
> That is there is no people with new ideas, better ideas,
> innovative ideas, more knowlege about certain subject matter,
> _anywhere_ but in the "Linux community".
>
> So in effect, there will never be an "outsider" who will
> come in to the "linux community" and change things around,
> no fresh ideas, no better (right?) way to do things.
>
> "The community" is not going to listen to anyone but only to
> already politically established members on _any_ subject
> matter, even technical, even from "outsiders" who work with
> the technology every day.
overreaction
>>>What _exactly_ does it mean "don't play well with others"?
>>
>>
>>It means not taking feedback, and working around rather than with the
>>SCSI core.
>
>
> So does this mean, that if I submit patches "fixing" (oops,
> not meant to hurt anyone's bal^w^w^wpride) SCSI Core, they
> will be accepted.
James and Christoph have been asking you to submit patches for a long
time now.
> Or do you want me to do "your way of SAS"?
> Maybe JB et al, should write the "Linux SAS spec" and
> then we can recommend this to T10.org, so they can scrap
> their version and use "the community's"?
You're over-reacting.
>>Then you don't understand the ->qc_{prep,issue} hooks. That should get
>>you 90% of the way there, if not 99%.
>
>
> But I have to simulate struct ata_port, Jeff.
>
> Which isn't so bad, but speaks about the design.
You have to provide a means to submit ATA commands and receive results,
no more or less.
>>>The code doesn't alter Linux SCSI or anyone else's behaviour.
>>>It only _provides_ SAS support to the kernel.
>>That's one of the problems: It should update the SCSI core.
> Thank you for admitting this -- you're the first and only
> member of "the community" (since I'm not a member apparently)
> to admit this.
James, Christoph and the rest of linux-scsi have been saying this over
and over again.
You need to update the SCSI core properly, rather than working around it.
Everybody knows the SCSI core is too SPI-centric, and you have been
given a recipe for fixing this.
Jeff
On 09/28/05 17:00, Jeff Garzik wrote:
> Luben Tuikov wrote:
>
>>Ideally SATL is just a _data transformation function_ and
>>getting to the ATA device is transport dependent.
>
>
> Incorrect. It needs to issue multiple ATA commands to emulate a single
> SCSI command, cache some state, and other details. Not purely data
> transformation.
Yes, this is right and I'm aware of it. I really, really,
had some wishful thinking.
> What needs to happen is that SPI-specific stuff in the SCSI core needs
> to be moved to SPI-specific transport code.
>
> Then all transports will be at an equal level, and the SCSI core will be
> fully transport-agnostic.
Yeah, I've been saying this for ages:
Read half way through my message from 2003 here:
http://marc.theaimsgroup.com/?l=linux-scsi&m=104257405408078&w=2
> "time and again" means that we have been specific multiple times.
> Re-read your emails from James and Christoph :)
So you're saying that they are right and I'm wrong,
and I should listen to them.
Which is _exactly_ what I've been pointing out:
"the community" thinks that only they are the
experts on the planet regarding new technologies,
thus they are right, engineers "outside the community"
are dead wrong and they should listen to what
"the community" says.
Shall I point out a multitude of emails whereby some
"community members" go out on _technology_ public lists
and start a flame war, until they are warned to behave
or be expelled? Is this what you mean the "they" are
right, and "we" are wrong?
The community calls specs "techno-gibberish"
and think that LUNs can be u64, that REQUEST SENSE
clears ACA, and that HCIL is here for ever, etc.
Excuse me if I simply ignore their "SCSI storage advice".
>>If you understood how different those architectures are,
>>you'd understand what I mean.
>
>
> James is wrong here.
Either you meant "Luben" here or you've been banned
forever from "the community" and your patches would never
ever be accepted.
> The "transport class" in reality winds up as a
> transport lib, in addition to simply exporting attributes.
>
> There will always be functions that are common to a transport.
> Christoph calls this "libsas", since software-driven SAS implementations
Look at the pictures (since its easier) in SAM/SAS/SPC.
It is not a "lib" it is a _layer_ in its own right,
which is completely and fully implemented in the FW
of an MPT-like (IOP in package) solution.
Access to _anything_ transport specific is _FIRMWARE_
specific and doesn't yield to unification as does
a SAS Transport Layer management.
The only unification you get is: "Here is a LLDD giving
you LUs to manage, and oh yeah, here is some FIRMWARE
dependent way to peek at the transport and transport
attributes".
>> I do not _know_ how to consolidate the completely broken
>> "design" set forth by JB and company.
>>
>>It is _completely_ not to SAM spec.
>
> Not true. Just because SCSI core lacks an explicit "execute SCSI
> command" RPC hook, does not imply that that capability is non-existent.
>
> Stare at the Scsi_Host_Template some more and you'll see it.
Well, then, how can I reply to this?
I say "1+1=2", you say "Not true. 1+1=3."
Show me the equivalence between the Scsi_Host_Template
and SAM, give me section references as well.
What I meant is that the place and design of JB's transport
attribute "blessing" is completely out of whack for SAM
abiding implementation.
Look at the pictures: the transport layer is _below_
the application client and the application client
is completely unaware of the transport.
Now lets translate (http://www.t10.org/scsi-3.gif) :
Command set drivers <--> sd, st, etc (application client)
SAM/SPC <--> SCSI Core to be
Transport layer <--> SAS (all others implemented in LLDD)
SDS <--> LLDD + Firmware
Interconnect <--> Firmware + hardware.
It is _this_ SAM architecture which allows you to say,
send SATA commands over SAS links (via STP), and do other
interesting things.
I guarantee you that any _new_ SCSI transport would yield
to a Transport Layer abstraction just as SAS does.
Since, this is what SAM _is_ (all about).
I don't mind James Bottomley entertaining his
"transport attribute" code, as long as he's not shoving
it down my throat (again because of pictures like the one
above).
As I've said before both implementations are _orthogonal_
and can coexist.
>>But an AIC-94xx and BCM8603 _is_ NOT a scsi_host material. It is just
>>an interface to the interconnect.
>
> A scsi_host is simply a container. You're being too literal.
By "too literal" do you mean "following specs too closely",
or do you mean "being realistic without tweaking things".
> Yes. We need to evolve the SCSI core to separate out SPI-specific
> pieces, to make it more transport-agnostic.
2003:
http://marc.theaimsgroup.com/?l=linux-scsi&m=104257405408078&w=2
> James and Christoph have been asking you to submit patches for a long
> time now.
Not patches to fix SCSI Core or to get "struct scsi_domain_device"
into SCSI Core or to get 64 bit LUNs into the kenrel.
They've been asking me for me to abandon the complete
SAS transport layer which I have, which is 1000 years ahead
of theirs and ahead of SCSI Core and to go and work
on LSI's and on "transport attributes".
Sorry, but SAM seems to disagree.
> James, Christoph and the rest of linux-scsi have been saying this over
> and over again.
They've never said it: why else do you think we do not
have 64 bit LUNS or why else do you think we have HCIL in
SCSI Core.
Instead, what James does is he goes off to implement
"transport attributes" and to submit patches to IDR
after I myself submitted patches to IDR? Why? So he can
undermine my patches? Well, as you can see I completely
removed IDR's usage from aic94xx. Now "the community" is happy.
> Everybody knows the SCSI core is too SPI-centric, and you have been
> given a recipe for fixing this.
I "have been given recipe for fixing this"?
Are you all right Jeff?
Yep, the recipe was given to me by people who think that
we should stay with HCIL, who have found purpose for
the "second channel" in HCIL, who think that REQUEST SENSE
clears ACA, who think that 64 bit LUN is just a waste, and
so forth with their antics.
So excuse me if I don't see or recognize the recipe
given to me. Mind pointing out a link? This way we
will have a hard coded evidence of what that recipe is.
And we can see the exact steps it outlines.
Thank you,
Luben
Hi all, hi Luben,
On Wed, Sep 28, 2005 at 04:56:20PM -0400, Luben Tuikov wrote:
(...)
> Ok, thanks Andre. Much appreciated.
>
> You are the first person to back me up _publicly_. Now if we
> can find a person from "the community" to do that, and get all
> the other people who've written me _privately_, we'd be in
> good shape.
I'm sure I'm not one of those who qualify best here, but having largely
contributed to Linux acceptance at critical points at a handful of big
customers here, I'd like to send some general feeling I get from there.
There are people buying expensive hardware. The type of hardware
that costs $100k for just a few CPUs. Those people don't buy "the
Adaptec XXX which runs best with Red Hat Enterprise" nor the "LSI
YYY which runs best with Solaris", they buy a few $100k systems
with 3 TB disk to store their monthly logs. They cannot even imagine
that the hardware in the $100k system will not be fully supported by
some recent OS, that's just plain silly. The OS cost is just a water
drop in the middle of this. When they install Solaris on it because
they're used to run it, it just works. When I sometimes just show
them that Solaris is not adequate for daily greps in logs, and I show
them how faster it is on a $1k Linux machine in the next rack, they
feel they can switch to it easily. But if they discover that this
system does not correctly support their $100k hardware, do you know
which one was is the crap ? the $300 Red Hat or the $100k hardware ?
[ oh, BTW, I forgot to tell you : they say "Red Hat", and not "Linux"
because it does not sound like what they long considered an OS for
tamagotchis - to use their own words - :-( ]
And when they go to adaptec site to find latest drivers and they only
find patches which forces them to find another Linux to install the
sources and guess how to patch and build, do you know which OS they
consider as hobbyist's ? The Red Hat ! (which they can call "Linux"
again then).
For those reasons, I could put Linux there on very specific places,
mostly firewalls and load-balancers. A self-made distro with kernel
2.4 with patch-o-matic still is one of the most powerful and reliable
firewalls around, and at only a few bucks. The same hardened install
is used for load-balancers with my proxy. Seeing that the proxies
have been stable for years, they bought between 50-100 RHEL licences.
But that's all. Nowhere you will find anything serious using Linux in
other areas. It's already a nightmare for them to get a hardware RAID
card working while they just have to click on stupid icons in Windows
to do the same. Right now, new Linux-based machines are turning back
to plain IDE. SCSI was too much boring for them and not needed to do
just networking. Period.
When they will buy hundreds of TB of SAS-based racks in the next few
years, and they will learn the hard way that Linux does not even see
them as disks, it will be too late to give my preferred OS a second
chance.
Hans Reiser once said that every software needs a complete rewrite
every 3 or 5 years (I don't precisely remember). I tend to agree
with him. Maybe it's time to completely rewrite the SCSI subsystem,
but maybe it will be too long, too risky and not worth the effort.
Maybe it can simply coexist with another new subsystem. This is what
Luben seems to have done : break no code, just bring a new subsystem
which should not even give the SCSI maintainer too much work if he
maintains it himself. At least I could understand some arguments against
Reiser4 because it touched the VFS, but here we have a perfect example
of something new which can live next to SCSI and probably some time
will replace it definitely. Jeff has done this with libata (it even
had to touch some pieces to coexist with piix4 and probably a few other
chips).
Having read the discussion from the start here a few days ago, I
believe that Luben maybe has not explained well to non-competent
people like me what the goal of his work is. I've looked at the GIF
on T10.org, but I think that the equivalent with what it currently
implemented in Linux would be worth doing. Maybe we would even
notice that current maintainers cannot agree on a same representation.
Maybe it will enlighten some of us about the poor error reporting,
the reasons why USB storage sometimes fails to assign a device when
plugging a flash, etc...
Luben, you seem to have enough knowledge to draw both diagrams
side-by-side :
- the T10 spec with colors on the boxes covered by your work
- the Linux view of SCSI
Perhaps we will see that current code can be extended without too
much work, or perhaps we will see that it's definitely a dead end
and that a new design will help a lot.
Anyway Luben, I fear that for some time, you'll have to provide
pre-patched sources as well as binary kernels to enterprise customers
who still try to get Linux working in production. I hope that this sad
experience will not discourage other vendors from trying to take the
opensource wagon, as it clearly brings fuel to closed-source drivers
at the moment (no need to argue).
Eventhough I don't have SAS, I sincerely hope that a quick and smart
solution will be found which keeps everyone's pride intact, as it
seems to matter much those days. In an ideal situation, 2.7 would
have been opened for a long time, and Luben's code would have been
discussed to death as a new development needed to be merged before
2.8. Right now, as 2.7 is 2.6.<odd>, probably that ideas can gem
before 2.6.15.
Just my personnal thoughts
Willy
PS: please don't CC me in return, I can read LKML. I haven't trimmed
the CC list as nobody has complained yet.
On Wed, 28 Sep 2005, Luben Tuikov wrote:
> On 09/28/05 15:45, Andre Hedrick wrote:
> > Luben, I have a vested interest in seeing SAS run via SCSI. So this means
> > you have one ex-demi-god from the world of maintainers looking to pull you
> > have towards the current path and open to ideas and willing to back a
> > better design and push it.
>
> Ok, thanks Andre. Much appreciated.
Luben,
I have a vested interest in the improvement of the Linux SCSI Core and
wider adoption and support for SATA II and SAS controllers with their
associated domains and transport.
> You are the first person to back me up _publicly_. Now if we
> can find a person from "the community" to do that, and get all
> the other people who've written me _privately_, we'd be in
> good shape.
Proving a better design with a migration path for integration is the key
for success; however, I am not the person to be the political voice in the
process. People will disagree in the process and the only counter to
remove blockage/adoption is in code.
James is king of the hill, and is reasonable to a point. James also
follows a model of generalization v/s specific design. Argh, this is not
going to be an easy one to explain or back away from now. Erm, inclusive
API design is where I am wanting to go with this thought.
Have you and company considered the approach of mapping to a library of
sorts?
Cheers,
Andre
Luben Tuikov wrote:
> The community calls specs "techno-gibberish"
> and think that LUNs can be u64, that REQUEST SENSE
> clears ACA, and that HCIL is here for ever, etc.
How many times do we have to repeat "HCIL dependencies should get moved
to SPI-specific transport code" before you listen?
>>>If you understood how different those architectures are,
>>>you'd understand what I mean.
>>
>>
>>James is wrong here.
>
>
> Either you meant "Luben" here or you've been banned
> forever from "the community" and your patches would never
> ever be accepted.
Quit being silly. I meant what I wrote. Though it turns out that your
interpretation of James's ideas was incorrect. James agrees that
"transport code" includes both lib and attributes, not attributes only.
> What I meant is that the place and design of JB's transport
> attribute "blessing" is completely out of whack for SAM
> abiding implementation.
By focusing on attributes, you miss the big picture. This is not about
attributes.
> Look at the pictures: the transport layer is _below_
> the application client and the application client
> is completely unaware of the transport.
>
> Now lets translate (http://www.t10.org/scsi-3.gif) :
> Command set drivers <--> sd, st, etc (application client)
> SAM/SPC <--> SCSI Core to be
> Transport layer <--> SAS (all others implemented in LLDD)
> SDS <--> LLDD + Firmware
> Interconnect <--> Firmware + hardware.
>
> It is _this_ SAM architecture which allows you to say,
> send SATA commands over SAS links (via STP), and do other
> interesting things.
>
> I guarantee you that any _new_ SCSI transport would yield
> to a Transport Layer abstraction just as SAS does.
>
> Since, this is what SAM _is_ (all about).
This is fundamental: SCSI specs dictate how this functions, not
necessarily what Linux code looks like.
The big picture is
device class <-> transport class
and everything falls out from there, including SAM.
Moving SPI (parallel SCSI, for those unfamiliar with the acronym) to
transport-specific code will eliminate legacy assumptions that you keep
complaining about.
Linux is about getting things done, not being religious about
specifications. You are way too focused on the SCSI specs, and missing
the path we need to take to achieve additional flexibility.
With Linux, it's all about evolution and the path we take.
> I don't mind James Bottomley entertaining his
> "transport attribute" code, as long as he's not shoving
> it down my throat (again because of pictures like the one
> above).
As long as you think James is merely talking about attributes, you're
just not getting it.
Transport classes are an abstraction which allows SAS to exist as a peer
to parallel SCSI, FC, and other acronyms.
>>>But an AIC-94xx and BCM8603 _is_ NOT a scsi_host material. It is just
>>>an interface to the interconnect.
>>
>>A scsi_host is simply a container. You're being too literal.
>
>
> By "too literal" do you mean "following specs too closely",
> or do you mean "being realistic without tweaking things".
I mean, paying too much attention to specs at the expense of
understanding how Linux code needs to be shaped.
>>James and Christoph have been asking you to submit patches for a long
>>time now.
>
>
> Not patches to fix SCSI Core or to get "struct scsi_domain_device"
> into SCSI Core or to get 64 bit LUNs into the kenrel.
>
> They've been asking me for me to abandon the complete
> SAS transport layer which I have, which is 1000 years ahead
> of theirs and ahead of SCSI Core and to go and work
> on LSI's and on "transport attributes".
They are asking you to help with the task of eliminating SPI
dependencies in the core, so that SAS can exist as a peer to other
transports.
>>James, Christoph and the rest of linux-scsi have been saying this over
>>and over again.
>
>
> They've never said it: why else do you think we do not
> have 64 bit LUNS or why else do you think we have HCIL in
> SCSI Core.
Repeating myself (and others): everybody wants HCIL stuff to move to
SPI-specific transport code.
That is the task that must be completed BEFORE transport layer for SAS
can be fully merged.
>>Everybody knows the SCSI core is too SPI-centric, and you have been
>>given a recipe for fixing this.
>
>
> I "have been given recipe for fixing this"?
>
> Are you all right Jeff?
>
> Yep, the recipe was given to me by people who think that
> we should stay with HCIL, who have found purpose for
> the "second channel" in HCIL, who think that REQUEST SENSE
> clears ACA, who think that 64 bit LUN is just a waste, and
> so forth with their antics.
For the nth time, everybody agrees HCIL should move to
transport-specific code.
And from past threads, everybody seems OK with moving to a 64-bit lun
representation.
> So excuse me if I don't see or recognize the recipe
> given to me. Mind pointing out a link? This way we
> will have a hard coded evidence of what that recipe is.
> And we can see the exact steps it outlines.
For the nth time:
http://marc.theaimsgroup.com/?l=linux-scsi&m=112487476527470&w=2
Jeff
Willy Tarreau wrote:
> And when they go to adaptec site to find latest drivers and they only
> find patches which forces them to find another Linux to install the
> sources and guess how to patch and build, do you know which OS they
> consider as hobbyist's ? The Red Hat ! (which they can call "Linux"
> again then).
Adaptec is unfortunately a special case. QLogic and other enterprise
vendors get along with quite well on $100k machines.
Both Luben and his predecessor, Justin Gibbs, were severely dissatisfied
with the SCSI core. Often they have raised valid issues that need
addressing, but their choice has been to work around or ignore existing
code (and maintainers), rather than work with it, and fix it.
> When they will buy hundreds of TB of SAS-based racks in the next few
> years, and they will learn the hard way that Linux does not even see
> them as disks, it will be too late to give my preferred OS a second
> chance.
Hardly. SAS support is coming, whether from Adaptec or someone else.
> Having read the discussion from the start here a few days ago, I
> believe that Luben maybe has not explained well to non-competent
> people like me what the goal of his work is. I've looked at the GIF
> on T10.org, but I think that the equivalent with what it currently
> implemented in Linux would be worth doing. Maybe we would even
> notice that current maintainers cannot agree on a same representation.
The current maintainers seem to agree on the path to transport independence.
> Anyway Luben, I fear that for some time, you'll have to provide
> pre-patched sources as well as binary kernels to enterprise customers
> who still try to get Linux working in production. I hope that this sad
> experience will not discourage other vendors from trying to take the
> opensource wagon, as it clearly brings fuel to closed-source drivers
> at the moment (no need to argue).
Yes, let's not argue this silliness. Other vendors don't seem to have
this level of problem.
> Eventhough I don't have SAS, I sincerely hope that a quick and smart
> solution will be found which keeps everyone's pride intact, as it
> seems to matter much those days. In an ideal situation, 2.7 would
> have been opened for a long time, and Luben's code would have been
> discussed to death as a new development needed to be merged before
> 2.8. Right now, as 2.7 is 2.6.<odd>, probably that ideas can gem
> before 2.6.15.
Sigh. This is not about pride. There's already a path to fixing up the
SCSI core to work nicely with SAS (and nicer with FC/iSCSI). Changing
to a new path midstream, in the middle of addressing the stated
problems, causes more delay, more harm than good.
Jeff
From: Jeff Garzik <[email protected]>
Date: Wed, 28 Sep 2005 19:22:53 -0400
> Both Luben and his predecessor, Justin Gibbs, were severely dissatisfied
> with the SCSI core. Often they have raised valid issues that need
> addressing, but their choice has been to work around or ignore existing
> code (and maintainers), rather than work with it, and fix it.
I'm in violent agreement here.
Justin was just as anti-social of an engineer as one could get. And,
when you put an ex-FreeBSD guy onto Linux driver maintainence, what in
the world could anyone expect. :-)
For example, instead of accepting that the symbol "current" is a
reserved symbol when compiling under the Linux kernel, he decided that
"sticking a square peg into a round hole" was a better way to deal
with this, and thus he put an "#undef current" into the adaptec driver
instead of simply renaming a structure member from "current" to
something else.
I don't know how else to define "control freak".
On Wed, Sep 28, 2005 at 07:04:31PM -0400, Jeff Garzik wrote:
> Linux is about getting things done, not being religious about
> specifications. You are way too focused on the SCSI specs, and missing
> the path we need to take to achieve additional flexibility.
>
> With Linux, it's all about evolution and the path we take.
Hmmm... I'm fine with "not being religious about specs", but I hope we
try to respect them as much as possible, because it's the only way to
get everything working and not get the finger pointed to when there's
a problem. When I put netfilter + window tracking in production 2 years
ago, there were a lot of drops (about 2% of sessions = ~40/s), because
shortcuts had been taken WRT rfc793 ("the specs"). Then, printing the
whole RFC+erratas was the only way to get the code working and
supporting the most bizarre cases that had previously been considered
stupid or impossible by the developpers (including me during the first
phase of the fixes).
I prefer that we stick to specs even if we just implement what we
*need* from them, leaving lots of blank boxes on the diagram, rather
than interprete them as we think would be better and get annoyed
everytime a vendor tries to adapt it to support his hardware.
> >By "too literal" do you mean "following specs too closely",
> >or do you mean "being realistic without tweaking things".
>
> I mean, paying too much attention to specs at the expense of
> understanding how Linux code needs to be shaped.
Both are true : Linux code needs to be shaped to match specs. We
must not spend time on what we don't need but we must respect the
model and layering, and that's true in any subsystem. Networking
for example, is very clean in this area. Even accelerations do
not break layering, it's just that some of the work can be pushed
down from layer to layer until one can process it (eg: checksums).
And when I worked on bonding, I did not have problems with it
breaking upper layers. I really believe that's important, it's
the first step to avoid spending time in debugging.
Cheers,
Willy
Dave,
Was it really necessary to this far and rude?
I heard the snow is falling and there is a fresh shipment of hash headed
out to the slopes, don't be late.
Not sure who to credit the following to:
When TOE's were introduced to Linux, there was a violent rejection of this
hardware because Linux is superior in the NetStack than any other possible
NetStack every created.
The point is there is a known history in Linux to reject things which
steps on peoples' egos.
Have a great ski trip.
Cheers,
Andre
On Wed, 28 Sep 2005, David S. Miller wrote:
> From: Jeff Garzik <[email protected]>
> Date: Wed, 28 Sep 2005 19:22:53 -0400
>
> > Both Luben and his predecessor, Justin Gibbs, were severely dissatisfied
> > with the SCSI core. Often they have raised valid issues that need
> > addressing, but their choice has been to work around or ignore existing
> > code (and maintainers), rather than work with it, and fix it.
>
> I'm in violent agreement here.
>
> Justin was just as anti-social of an engineer as one could get. And,
> when you put an ex-FreeBSD guy onto Linux driver maintainence, what in
> the world could anyone expect. :-)
>
> For example, instead of accepting that the symbol "current" is a
> reserved symbol when compiling under the Linux kernel, he decided that
> "sticking a square peg into a round hole" was a better way to deal
> with this, and thus he put an "#undef current" into the adaptec driver
> instead of simply renaming a structure member from "current" to
> something else.
>
> I don't know how else to define "control freak".
> -
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> Please read the FAQ at http://www.tux.org/lkml/
>
From: Andre Hedrick <[email protected]>
Date: Wed, 28 Sep 2005 22:30:58 -0700 (PDT)
> Not sure who to credit the following to:
>
> When TOE's were introduced to Linux, there was a violent rejection of this
> hardware because Linux is superior in the NetStack than any other possible
> NetStack every created.
>
> The point is there is a known history in Linux to reject things which
> steps on peoples' egos.
In that case, it is indeed a vendor trying to shove their particular
solution down our throats. They never even attempt to try out the
alternatives, and we've even gone through the trouble of coming up
with several. And they do this because their whole buisness model is
all about their scheme to the exclusion of anything else, not because
what they have is better.
On Thu, 2005-09-29 at 06:04 +0200, Willy Tarreau wrote:
> On Wed, Sep 28, 2005 at 07:04:31PM -0400, Jeff Garzik wrote:
> > Linux is about getting things done, not being religious about
> > specifications. You are way too focused on the SCSI specs, and missing
> > the path we need to take to achieve additional flexibility.
> >
> > With Linux, it's all about evolution and the path we take.
>
> Hmmm... I'm fine with "not being religious about specs", but I hope we
> try to respect them as much as possible
a spec describes how the hw works... how we do the sw piece is up to
us ;)
(I know the scsi stuff also provides sort of a reference "here is how
you can do it in sw" but I see that more as you "you need this
functionality" not "you need this exact architecture in your software")
On 09/28/05 18:35, Willy Tarreau wrote:
> There are people buying expensive hardware. The type of hardware
> that costs $100k for just a few CPUs. Those people don't buy "the
> Adaptec XXX which runs best with Red Hat Enterprise" nor the "LSI
> YYY which runs best with Solaris", they buy a few $100k systems
> with 3 TB disk to store their monthly logs. They cannot even imagine
> that the hardware in the $100k system will not be fully supported by
> some recent OS, that's just plain silly. The OS cost is just a water
> drop in the middle of this. When they install Solaris on it because
> they're used to run it, it just works. When I sometimes just show
> them that Solaris is not adequate for daily greps in logs, and I show
> them how faster it is on a $1k Linux machine in the next rack, they
> feel they can switch to it easily. But if they discover that this
> system does not correctly support their $100k hardware, do you know
> which one was is the crap ? the $300 Red Hat or the $100k hardware ?
> [ oh, BTW, I forgot to tell you : they say "Red Hat", and not "Linux"
> because it does not sound like what they long considered an OS for
> tamagotchis - to use their own words - :-( ]
Yes, all true.
Sadly, most developers here do not _use_ Linux, or are at least
shielded from using Linux, in a _business_.
All the while, Linux _development_, seems to follow some kind
"yours/mine", "gimme that/take that" kindergarten kind of way.
The reason I'm saying this is that _every_ successful entity
(person, corporation, etc) knows that in order to _survive_
it needs to _quickly adapt to new things_: new technologies,
new trends, new fads, etc.
But eventually, when entities get too successful, they
get _complacent_ (with themselves) and turning _away_
from their younger style of functioning (of absolving
everything in order to get successful in the first place).
All this, of course, it the _natural_ way of history. We
see it when studying History, and we see it every day
when reading the Technology section of our favourite
publication.
Some companies are _fiercly_ trying to beat this _natural_
course of History, into turning 180 degrees from their mindset
every single year in order to chase the latest technology, the
latest fad, in order to please customers and stay on top.
I wish Linux would return to its roots.
> And when they go to adaptec site to find latest drivers and they only
> find patches which forces them to find another Linux to install the
> sources and guess how to patch and build, do you know which OS they
> consider as hobbyist's ? The Red Hat ! (which they can call "Linux"
> again then).
OMG, "hobbyist" -- this so perfectly describes it! LOL
So now, if there is any coroprate management from RH here reading
this they'd take heed in this.
Linux _development_ needs to catch up to Linux _deployment_.
Currently they are two different worlds.
> Hans Reiser once said that every software needs a complete rewrite
> every 3 or 5 years (I don't precisely remember). I tend to agree
> with him. Maybe it's time to completely rewrite the SCSI subsystem,
> but maybe it will be too long, too risky and not worth the effort.
> Maybe it can simply coexist with another new subsystem. This is what
Now _this_ is a smart suggestion: it wouldn't break legacy hardware
_and_ it would give Linux SCSI a fresh start.
Next year, your new serverboard wouldn't have any of those old
cumbersome storage chips to worry about. It would have only one
storage chip which could do SAS and SATA and that'd be that.
Why would anyone need this fat, old semanticaly overloaded,
SPI-centric SCSI Core?
> Luben, you seem to have enough knowledge to draw both diagrams
> side-by-side :
> - the T10 spec with colors on the boxes covered by your work
> - the Linux view of SCSI
>
> Perhaps we will see that current code can be extended without too
> much work, or perhaps we will see that it's definitely a dead end
> and that a new design will help a lot.
Yes, I'll get that jpg and try to color it, but there's
also a lot of other components (Interconnect, SDS,
Application Client) which are not visible in this interconnect.
I'll try to get something descriptive.
> Anyway Luben, I fear that for some time, you'll have to provide
> pre-patched sources as well as binary kernels to enterprise customers
> who still try to get Linux working in production. I hope that this sad
> experience will not discourage other vendors from trying to take the
> opensource wagon, as it clearly brings fuel to closed-source drivers
> at the moment (no need to argue).
Foremost, this experience reminds other vendors that Linux
_development_ model is _not_ en par with their Linux _deployment_
model (i.e. for a business).
Many things are left to the whim of developers whose educational
and technical background could be in question especially when
your only communication with them is via email.
I mean -- I don't even know the _age_ ballpark of most developers
here. (Other than ones I've seen at OLS.) For all I know I could
be having a discussion with a 9 year old kid, repeating SAM and SPC
references over and over again.
I just don't see the technologically savvy and _open_ community
here.
> Eventhough I don't have SAS, I sincerely hope that a quick and smart
> solution will be found which keeps everyone's pride intact, as it
I'm not shoving my solution down the throats of LSI or James or
Christoph. Why?
- because the technologies are different,
- beacause I'm following a SAM model, they are not.
- and because I'm not changing anybody else's code but integrating
with it.
(Jeff, I know that on the 3rd point, you'd say "That's the problem,
you should be improving SCSI Core", and I know that if I had been
changing other people's code, you'd say "You should not change
other people's code", so it's a win-win-manipulative situation
for you. I'm aware of that, spare your keystrokes.)
This is all _fine_ with me as long as they are not shoving down
my throat their solution.
I wonder the pride to technological merit ratio in Linux SCSI.
> seems to matter much those days. In an ideal situation, 2.7 would
> have been opened for a long time,
Maybe things are slowing down for Linux? Attitude? Complacency?
History? Who knows?
> and Luben's code would have been
> discussed to death as a new development needed to be merged before
We did have a Storage BOF (Birds Of Feather) at the Ottawa Linux
Symposium (OLS) in July this year. It was called "SAS" and someone
made me do the presentation. Drawing on a white board several layers
and how they communicate with each other, how things work, why they
work the way they work, how they are shown and represented and why.
The response I got from James and Chritsoph was:
"The sysfs tree would be too deep."
The next day I learned that such argument is bogus and a sysfs
tree can be as deep as the representation calls for.
So you see, _this_ is where we started -- with _this_ kind
of argument: "The sysfs tree would be too deep."
BTW, James already had already had my code for about two
weeks before OLS.
Luben
Luben Tuikov wrote:
> All the while, Linux _development_, seems to follow some kind
> "yours/mine", "gimme that/take that" kindergarten kind of way.
> The reason I'm saying this is that _every_ successful entity
> (person, corporation, etc) knows that in order to _survive_
> it needs to _quickly adapt to new things_: new technologies,
> new trends, new fads, etc.
The core problem is that a SAM-friendly path to SAS has already been
chosen -- transport classes -- and your driver isn't following this path.
If we choose a new path every six months, we'll never arrive at the
destination.
> Some companies are _fiercly_ trying to beat this _natural_
> course of History, into turning 180 degrees from their mindset
> every single year in order to chase the latest technology, the
> latest fad, in order to please customers and stay on top.
>
> I wish Linux would return to its roots.
Linux today is the most successful its ever been. This system, however
strange it may seem, does work.
>>Hans Reiser once said that every software needs a complete rewrite
>>every 3 or 5 years (I don't precisely remember). I tend to agree
>>with him. Maybe it's time to completely rewrite the SCSI subsystem,
>>but maybe it will be too long, too risky and not worth the effort.
>>Maybe it can simply coexist with another new subsystem. This is what
>
>
> Now _this_ is a smart suggestion: it wouldn't break legacy hardware
> _and_ it would give Linux SCSI a fresh start.
>
> Next year, your new serverboard wouldn't have any of those old
> cumbersome storage chips to worry about. It would have only one
> storage chip which could do SAS and SATA and that'd be that.
> Why would anyone need this fat, old semanticaly overloaded,
> SPI-centric SCSI Core?
The rest of the Linux-SCSI devs are trying to make it less SPI-centric.
Rather than just complain, we're doing something about it.
> Foremost, this experience reminds other vendors that Linux
> _development_ model is _not_ en par with their Linux _deployment_
> model (i.e. for a business).
>
> Many things are left to the whim of developers whose educational
> and technical background could be in question especially when
> your only communication with them is via email.
Background is irrelevant. Only results matter. Linux is a meritocracy.
> I'm not shoving my solution down the throats of LSI or James or
> Christoph. Why?
> - because the technologies are different,
> - beacause I'm following a SAM model, they are not.
> - and because I'm not changing anybody else's code but integrating
> with it.
>
> (Jeff, I know that on the 3rd point, you'd say "That's the problem,
> you should be improving SCSI Core", and I know that if I had been
> changing other people's code, you'd say "You should not change
> other people's code", so it's a win-win-manipulative situation
> for you. I'm aware of that, spare your keystrokes.)
Spare me your paranoia. I've been 100% honest with you in every email
I've written.
You -should- change other people's code. That's how Linux gets better.
When I chose a better path for libata's error handling, the first step
in that process was changing the locking, and modifying almost every
$!#$@! SCSI driver in the kernel. Rather than forever complaining about
an outdated SCSI layer, I stepped up and fixed things.
>>seems to matter much those days. In an ideal situation, 2.7 would
>>have been opened for a long time,
>
>
> Maybe things are slowing down for Linux? Attitude? Complacency?
> History? Who knows?
SCSI work is speeding up. The SCSI core has come a -long- way in the
past couple years. 2.6.x SCSI is light years ahead of 2.4.x SCSI.
Jeff
On 09/28/05 18:43, Andre Hedrick wrote:
> I have a vested interest in the improvement of the Linux SCSI Core and
> wider adoption and support for SATA II and SAS controllers with their
> associated domains and transport.
Us and other companies too.
> Proving a better design with a migration path for integration is the key
> for success; however, I am not the person to be the political voice in the
Yes, _it is_ the key to success.
> James is king of the hill, and is reasonable to a point. James also
Which "hill" is the question. If he were reasonable, he'd
understand that the two technologies _are_ completely different and
distinct and he'd not try to shove HIS solution down my throat.
Just as I do not shove my solution in his throat.
The whole point is that MPT-based (IOP on package) solutions
_do not_ need a Transport Layer, since that Transport Layer
_is_ already present: in the firmware _and_ access to it
is _firmware_ dependent.
All the while open transport solutions (ours and apparently
Broadcoms') _expose_ the whole infrastructure and _give_ you
the chip as an interface to the interconnect. So you actually
_need_ a transport management layer. Now that transport
management layer sits _below_ SCSI Core and SCSI Core is
_unaware_ of the transport.
> follows a model of generalization v/s specific design. Argh, this is not
> going to be an easy one to explain or back away from now. Erm, inclusive
> API design is where I am wanting to go with this thought.
You can have inclusive API design for chips like AIC-94xx and BCM8603,
because they <see paragraph above>.
MPT-based ones <see paragraph above> would also use inclusive
design _for MPT-based chips_.
> Have you and company considered the approach of mapping to a library of
> sorts?
Hmm, it is not a library.
It is a layer, again, because of what the chip actually is, and because
of what it implements.
Take a look at the announcement text, I do give some description there
and in the code the drivers/scsi/sas-class/README file describes
the event/managment infrastructure. Also you can take a look at the code.
http://linux.adaptec.com/sas/
What you'll see in the code is:
hardware implementation (interconnect, SAM 4.15, 1.3)
firmware implementation (interconnect, SDS, SAM 4.6, 1.3)
LLDD (SAM, section 5, 6, 7)
Transport Layer (SAM 4.15, SAS)
SCSI Core (SAM section 4,5,8)
Commmand Sets (SAM section 1)
A very nice explanation in latest SAM4r03,
section 4.15 The SCSI model for distributed communications.
Now for MPT based solutions you have:
LLDD (SAM, section 5, 6, 7)
SCSI Core (SAM section 4,5,8)
Commmand Sets (SAM section 1)
You see? No Transport Layer between LLDD and SCSI Core!
Why? Because all this work is done in FIRMWARE!
That is, the LLDD exports the LUs right into SCSI Core,
So in effect there is _no_ need for a software Transport
Layer.
Can we have a video/tele conference on this?
Luben
Luben Tuikov wrote:
> hardware implementation (interconnect, SAM 4.15, 1.3)
> firmware implementation (interconnect, SDS, SAM 4.6, 1.3)
> LLDD (SAM, section 5, 6, 7)
> Transport Layer (SAM 4.15, SAS)
> SCSI Core (SAM section 4,5,8)
> Commmand Sets (SAM section 1)
Transport class + libsas achieves this.
Maybe I will have to demonstrate using code...
Jeff
On 09/29/05 03:44, Arjan van de Ven wrote:
>
> a spec describes how the hw works... how we do the sw piece is up to
> us ;)
Arjan, I'll be your best friend here:
Never say this in public or in an intervew.
Hardware folks needs to work with software folks and
software folks need to work with hardware folks.
This is what makes good design.
Luben
El Thu, 29 Sep 2005 10:33:03 -0400,
Luben Tuikov <[email protected]> escribi?:
> The reason I'm saying this is that _every_ successful entity
> (person, corporation, etc) knows that in order to _survive_
> it needs to _quickly adapt to new things_: new technologies,
> new trends, new fads, etc.
[...]
> I wish Linux would return to its roots.
I don't know how things were when you started using linux but linux
has never been about that AFAIK. People usually buys windows
licenses for that ;)
> here. (Other than ones I've seen at OLS.) For all I know I could
> be having a discussion with a 9 year old kid, repeating SAM and SPC
> references over and over again.
Oh well. May be Christoph and James are behaving like 9-years-old
kids, but if that's true you're NOT BEING DIFFERENT than them if
you look a bit to your mails.
You can be pretty sure that at this stage everyone is looking you as a
9-years-old kid who is raving because his mother don't buy him a
candy. Maybe they're looking james and christoph int he same way
aswell, but that's their issue.
Luben Tuikov wrote:
> On 09/29/05 03:44, Arjan van de Ven wrote:
>
>>a spec describes how the hw works... how we do the sw piece is up to
>>us ;)
>
>
> Arjan, I'll be your best friend here:
> Never say this in public or in an intervew.
It's hard-earned experience. We constantly have to teach hardware
vendors how to write good drivers.
At some point you have to step away from the spec, and ask yourself what
makes sense for Linux. I've already had to poke T10 when they put silly
things in the SAT spec.
As a tangent, I already have a design for a Linux filesystem that makes
use of SCSI object-based storage (to James's horror, no doubt :)). It's
a fun thing to ponder.
> Hardware folks needs to work with software folks and
> software folks need to work with hardware folks.
Certainly. The historical disconnect is where hardware vendors tend to
presume They Know Best, when in reality it needs to be an equal
tradeoff. Hardware vendors must admit they don't know Linux, and Linux
developers must admit that hardware vendors know their own hardware
better than anyone else.
Jeff
On Thu, 2005-09-29 at 10:33 -0400, Luben Tuikov wrote:
[...]
> Linux _development_ needs to catch up to Linux _deployment_.
That is probably the root and single cause of quality problems in
companies: Deployment folks (read: sales) set the delivery date (and get
the bonus for selling) and the rest (read: tech folks) have to follow,
no matter what (and get the blame for being late and buggy).
Or why do you think that MSFT has such quite crappy software?
> Currently they are two different worlds.
ACK - in the commercial world (and the bigger the company the worse
because sales people are far more distant from the tech people).
[ software rewrite ]
> > Maybe it can simply coexist with another new subsystem. This is what
>
> Now _this_ is a smart suggestion: it wouldn't break legacy hardware
> _and_ it would give Linux SCSI a fresh start.
>
> Next year, your new serverboard wouldn't have any of those old
> cumbersome storage chips to worry about. It would have only one
> storage chip which could do SAS and SATA and that'd be that.
> Why would anyone need this fat, old semanticaly overloaded,
> SPI-centric SCSI Core?
Then submit your driver as a (separate) block device in parallel to the
existing SCSI subsystem. People will use it for/with other parts if it
makes sense (and you - as the maintainer - accept their patches). And in
a few years the "old" SCSI core fades out as legacy drives fade out (or
they will happily coexist forever).
The point is: If *you* want it that way, *you* must go that way (and do
not expect others to do it just that *you* get *your* driver merged).
You are the maintainer of the new stuff and (almost) everything will
work as you want.
It might not be the cleanest or most elegant solution in the world, but
if it works, who cares and why?
Where is now the real problem?
I can't see one.
Bernd
--
Firmix Software GmbH http://www.firmix.at/
mobil: +43 664 4416156 fax: +43 1 7890849-55
Embedded Linux Development and Services
On 09/29/05 10:48, Jeff Garzik wrote:
> Luben Tuikov wrote:
>
>>All the while, Linux _development_, seems to follow some kind
>>"yours/mine", "gimme that/take that" kindergarten kind of way.
>>The reason I'm saying this is that _every_ successful entity
>>(person, corporation, etc) knows that in order to _survive_
>>it needs to _quickly adapt to new things_: new technologies,
>>new trends, new fads, etc.
>
>
> The core problem is that a SAM-friendly path to SAS has already been
> chosen -- transport classes -- and your driver isn't following this path.
Man you never stop do you?
I repeat again (I'll cut and paste this):
When JB's transport classes were introduced there was NO MENTIONING
of SAS. THE REASON THEY WERE INTRODUCED INTO LINUX BY JB IS TO
ACCOMODATE MPT-based SOLUTIONS FROM TWIDDLING WITH IOCTLS!
How do I know this: simple: JB's "transport attributes" have
NOTHING to do with SAM.
They break the layering architecture for one, and are
ATTRIBUTE EXPORTING FACILITY for another.
I understand that you want to preserve your friend's
bal^w^w^wpride but, lets face it:
I do not try to shove my solution down JB's throat.
As I've said many times: they are different due to
the *technology they represent*, which differs in
implmentation, and they can coexist!
If you can say this statement:
"The core problem is that a SAM-friendly path to SAS
has already been chosen -- transport classes -- and
your driver isn't following this path."
This means that you have NO CLUE ABOUT SAS or SAM!
I certainly hope that things would improve once you
start reading specs and talking to the engineers
who designed BCM8603. (If you are still going to
write their driver for them.)
> If we choose a new path every six months, we'll never arrive at the
> destination.
No one is choosing a new path every six months.
And this isn't a new path for _everybody_ to follow, it is only
for LLDD who need a transport layer to drive the transport
they expose an interface to.
I'm _not_ choosing a new path. No one is required to
"follow" this. This is just _technology_ for LLDD who _need_
a management layer, and who _cannot_ inteface with a high
level such as SCSI Core.
> Linux today is the most successful its ever been. This system, however
> strange it may seem, does work.
And as you can see, Linux today is the most anal retentive as it
has ever been (e.g. SAS, reiser4, and other (revolutionary) technologies).
Remember, you can only go _down_ from the top. So please
do not say
"Linux is the most successful it's ever been."
It's too immature as it means that it would either go down
or that it cannot become even _more_ successful.
> The rest of the Linux-SCSI devs are trying to make it less SPI-centric.
> Rather than just complain, we're doing something about it.
Oh this is such a political sap, Jeff -- I cannot believe
you're actually saying this.
Who are you pleasing? Your management?
I've been asking for movement AWAY from HCIL from early
2003, when you were writing libata, remember? Or do you
want a link to marc.10east.com?
Stop this political BS sap "we're doing something about it", please.
I suggested native scsi_target support so long ago, only to get
snuffed at.
>>Many things are left to the whim of developers whose educational
>>and technical background could be in question especially when
>>your only communication with them is via email.
>
> Background is irrelevant. Only results matter. Linux is a meritocracy.
Single line statements like this with 0-content, FUD-like,
only for you to reply right away, do not _contribute_ anything.
You're just throwing sand in the eyes of managament reading this.
> Spare me your paranoia. I've been 100% honest with you in every email
> I've written.
>
> You -should- change other people's code. That's how Linux gets better.
I doubt you've ever been honest with me.* The reason is that
you are trying to push down my throat JB's "transport classes",
all the while you're saying I'm supposed to change other people's
code?
Just see how you started this email (above).
So please, don't try to get out of any situation turning 180
degrees around.
* Well, maybe you _are_ 100% honest with me. Maybe you really
do believe that your friend JB's "transport _attributes_" code
has anything to do with SAM.
> When I chose a better path for libata's error handling, the first step
> in that process was changing the locking, and modifying almost every
> $!#$@! SCSI driver in the kernel. Rather than forever complaining about
> an outdated SCSI layer, I stepped up and fixed things.
I flipped a card: "You'll get a promotion soon!".
What else can I reply to a self-gratifying statment like this?
Can I reply with someting like: "See my SAS stuff -- how it
truthfully represents the whole domain and gives complete
control of it over to user space? See?"
> SCSI work is speeding up. The SCSI core has come a -long- way in the
> past couple years. 2.6.x SCSI is light years ahead of 2.4.x SCSI.
Well, this only tell you the (bad) state of affairs of _2.4.x_ SCSI.
This does _not_ tell you the state of affairs of 2.6.x SCSI.
2.6.x SCSI is light years _behind_ SAM.
Luben
On 09/29/05 11:08, Jeff Garzik wrote:
> Luben Tuikov wrote:
>
>> hardware implementation (interconnect, SAM 4.15, 1.3)
>> firmware implementation (interconnect, SDS, SAM 4.6, 1.3)
>> LLDD (SAM, section 5, 6, 7)
>> Transport Layer (SAM 4.15, SAS)
>> SCSI Core (SAM section 4,5,8)
>> Commmand Sets (SAM section 1)
>
>
> Transport class + libsas achieves this.
This is *WRONG*. (see below)
And it doesn't "achieve" this. Stop the FUD.
There is a _reason_ why it is the way it is.
> Maybe I will have to demonstrate using code...
Jeff,
There is a _reason_ why technical people separate concepts
in _layers_.
There is a _reason_ why technical people use Object Oriented
Paradigms describing models and design.
Do you know _what_ that reason is?
Or should I leave you to "demonstrate with code"?
Seeing that you keep _persisting_ in your ways,
I'll leave it for you to "enrich" Linux SCSI in
your "demonstrate with code".
Luben
On 09/29/05 11:17, Bernd Petrovitsch wrote:
>
> Then submit your driver as a (separate) block device in parallel to the
> existing SCSI subsystem. People will use it for/with other parts if it
SAS is ultimately SCSI. I'll just have to write my own SCSI core.
_We_ together can do this in parallel to the old SCSI Core.
This is the whole idea.
> makes sense (and you - as the maintainer - accept their patches). And in
You see, at my age and my situation, I no longer see this as
"my balls - your balls". What matters to me is good design,
quality code, customer satisfaction, bottom line.
E.g. I'm quite a liberal person and I wouldn't block
or stop new technologes from going into Linux on the basis
and merit of my not understanidn that particular new technology.
The bottom line is not "my balls - your balls" but the wide
spread use of Linux and "storage OS of choice". Not "hobbyist
OS of choice" and not "let me play Robin Hood".
> a few years the "old" SCSI core fades out as legacy drives fade out (or
> they will happily coexist forever).
Yep, I've been saying this since 2002. On the linux-scsi ML.
> The point is: If *you* want it that way, *you* must go that way (and do
> not expect others to do it just that *you* get *your* driver merged).
> You are the maintainer of the new stuff and (almost) everything will
> work as you want.
And this is the problem: *you* and "the community" see things in
*this* way: "your balls - my balls", "yours/mine".
While I see things like this: new technology, absolve, use, move on.
As to your comment above, it's not about how *I* see things.
It's about how things _actually_ *are*:
http://www.t10.org/ftp/t10/drafts/sam4/sam4r03.pdf
> It might not be the cleanest or most elegant solution in the world, but
> if it works, who cares and why?
Turn the table around: can _I_ pose this question to JB and Christoph?
(since they are the ones who think this of SAM/SPC)
> Where is now the real problem?
> I can't see one.
Me neither.
Luben
Luben Tuikov wrote:
> of SAS. THE REASON THEY WERE INTRODUCED INTO LINUX BY JB IS TO
> ACCOMODATE MPT-based SOLUTIONS FROM TWIDDLING WITH IOCTLS!
Wrong. This shows you fundamentally don't understand transport classes
at all.
AFAIK, the first transport class was FC, for qla2xxx.
Read the code to see how FC avoids the SPI-centric scan -- an example of
transport independence.
> How do I know this: simple: JB's "transport attributes" have
> NOTHING to do with SAM.
>
> They break the layering architecture for one, and are
> ATTRIBUTE EXPORTING FACILITY for another.
Transport class == transport layer. Eventually this will sink in.
Transport class allows for complete transport independence, be it SAS,
FC, iSCSI, or other.
> And as you can see, Linux today is the most anal retentive as it
> has ever been (e.g. SAS, reiser4, and other (revolutionary) technologies).
>
> Remember, you can only go _down_ from the top. So please
> do not say
> "Linux is the most successful it's ever been."
We've still got all that Microsoft and old-Unix marketshare to steal :)
> It's too immature as it means that it would either go down
> or that it cannot become even _more_ successful.
>
>
>>The rest of the Linux-SCSI devs are trying to make it less SPI-centric.
>> Rather than just complain, we're doing something about it.
>
>
> Oh this is such a political sap, Jeff -- I cannot believe
> you're actually saying this.
I'm merely stating I'm submitting patches to clean up SCSI core. Others
have submitted far more patches than I. And further patches to SCSI
core are needed to properly integrate SAS as a transport completely
independent from SPI. I'm going to be putting time and effort into
moving the SCSI core away from SPI, so that SAS can be properly integrated.
All I've seen from you is
(a) complaints that the SCSI core is too SPI-centric
(b) a solution that does nothing to fix this
> Who are you pleasing? Your management?
My goal is Linux. Always has been. I put quality of Linux code, and
giving features to Linux users, above all else. Have been doing so
regardless of who employs me, for many years now.
Maybe one day I will be independently wealthy, be a completely
independent Linux maintainer, and then people will have to find
something other than Red Hat as the reason for why their code is
receiving criticism.
> I doubt you've ever been honest with me.* The reason is that
> you are trying to push down my throat JB's "transport classes",
> all the while you're saying I'm supposed to change other people's
> code?
To get a fully SPI-independent SCSI core, we must change other people's
code. That's the way Linux works. We evolve the existing code.
Jeff
On 09/29/05 11:20, Jeff Garzik wrote:
>>Arjan, I'll be your best friend here:
>>Never say this in public or in an intervew.
>
>
> It's hard-earned experience. We constantly have to teach hardware
> vendors how to write good drivers.
I'm sure you have. Hardware vendors are lost without
Jeff, James Bottomley and Christoph.
You see, it is because of your _enormous_ ego as shown
above, that the code is being blocked.
> At some point you have to step away from the spec, and ask yourself what
> makes sense for Linux.
I'm sure -- flush interoperability down the drain.
> I've already had to poke T10 when they put silly
> things in the SAT spec.
Surely they are lost without you.
> As a tangent, I already have a design for a Linux filesystem that makes
> use of SCSI object-based storage (to James's horror, no doubt :)). It's
> a fun thing to ponder.
Ok, so the way I see it you want to show who has got
the bigger balls?
Jeff, I have *worked* on a Linux OBD-based filesystem.
Are you going to stop this self-gratifying stuff?
>>Hardware folks needs to work with software folks and
>>software folks need to work with hardware folks.
>
> Certainly. The historical disconnect is where hardware vendors tend to
> presume They Know Best, when in reality it needs to be an equal
> tradeoff. Hardware vendors must admit they don't know Linux, and Linux
> developers must admit that hardware vendors know their own hardware
> better than anyone else.
Reflection of above:
The historical disconnect is where "the community" tend to
presume They Know Best, when in reality it needs to be an equal
tradeoff. "The community" must admit they don't know hardware,
and hardware developers must admit that "the community" know their
own code better than anyone else.
Jeff, if you had started looking at the design and firmware
of any new SCSI storage chip, you'd see how incredibly similar
it is to the transport it defines, and thus to SAM, since the
transport itself has to comply with SAM for interoperability
(TMF and all).
Linux SCSI does _not_ need to do "its own thing". There are
perfectly well defined specs, telling you how things are
conceptually _and_ in the physical world.
In order to control those objects, you need to represent
them internally (you can learn this either in neuroscience
class or in OOD & OOP comp sci classes) as you can see has
been done in the SAS Transport Layer code.
So if you want _better control_, higher quality you need
to invent _your own_ stuff as _little as possible_ and
represent things as they are.
Luben
Luben Tuikov wrote:
> On 09/29/05 11:17, Bernd Petrovitsch wrote:
>
>>Then submit your driver as a (separate) block device in parallel to the
>>existing SCSI subsystem. People will use it for/with other parts if it
>
>
> SAS is ultimately SCSI. I'll just have to write my own SCSI core.
> _We_ together can do this in parallel to the old SCSI Core.
You should have stated this plainly, from the start.
If you want to do your own SCSI layer, you need to do it at the block
layer rather than poking around drivers/scsi/
Jeff
On 09/29/05 12:56, Jeff Garzik wrote:
> Luben Tuikov wrote:
>
>>On 09/29/05 11:17, Bernd Petrovitsch wrote:
>>
>>
>>>Then submit your driver as a (separate) block device in parallel to the
>>>existing SCSI subsystem. People will use it for/with other parts if it
>>
>>
>>SAS is ultimately SCSI. I'll just have to write my own SCSI core.
>>_We_ together can do this in parallel to the old SCSI Core.
>
>
> You should have stated this plainly, from the start.
>
> If you want to do your own SCSI layer, you need to do it at the block
> layer rather than poking around drivers/scsi/
So now you are saying that I should _not_ poke at drivers/scsi?
(as I haven't done)
Are you going to make up your mind?
Luben
Luben Tuikov wrote:
> On 09/29/05 12:56, Jeff Garzik wrote:
>
>>Luben Tuikov wrote:
>>
>>
>>>On 09/29/05 11:17, Bernd Petrovitsch wrote:
>>>
>>>
>>>
>>>>Then submit your driver as a (separate) block device in parallel to the
>>>>existing SCSI subsystem. People will use it for/with other parts if it
>>>
>>>
>>>SAS is ultimately SCSI. I'll just have to write my own SCSI core.
>>>_We_ together can do this in parallel to the old SCSI Core.
>>
>>
>>You should have stated this plainly, from the start.
>>
>>If you want to do your own SCSI layer, you need to do it at the block
>>layer rather than poking around drivers/scsi/
>
>
> So now you are saying that I should _not_ poke at drivers/scsi?
> (as I haven't done)
>
> Are you going to make up your mind?
Are you: are you going to rewrite the SCSI core, or work to improve the
existing one?
Your choice, not mine. Your time, not mine.
Jeff
Luben Tuikov wrote:
> On 09/29/05 11:20, Jeff Garzik wrote:
>
>>>Arjan, I'll be your best friend here:
>>>Never say this in public or in an intervew.
>>
>>
>>It's hard-earned experience. We constantly have to teach hardware
>>vendors how to write good drivers.
>
>
> I'm sure you have. Hardware vendors are lost without
> Jeff, James Bottomley and Christoph.
>
> You see, it is because of your _enormous_ ego as shown
> above, that the code is being blocked.
No, I was referring to things such as, e.g.
http://people.redhat.com/arjanv/olspaper.pdf
http://people.redhat.com/arjanv/OLS.pdf
It has nothing to do with ego, just hard-won experience.
There are bunches of hardware vendors who have their patches merged
immediately after posting. They get it. They have internalized the
reasons why Linux drivers look the way they do.
>>As a tangent, I already have a design for a Linux filesystem that makes
>>use of SCSI object-based storage (to James's horror, no doubt :)). It's
>>a fun thing to ponder.
>
>
> Ok, so the way I see it you want to show who has got
> the bigger balls?
>
> Jeff, I have *worked* on a Linux OBD-based filesystem.
>
> Are you going to stop this self-gratifying stuff?
Oh good grief. It was an example, silly. Trying to lighten the mood, even.
Jeff
On Thu, 2005-09-29 at 12:33 -0400, Luben Tuikov wrote:
> On 09/29/05 11:17, Bernd Petrovitsch wrote:
[...]
> > Then submit your driver as a (separate) block device in parallel to the
> > existing SCSI subsystem. People will use it for/with other parts if it
>
> SAS is ultimately SCSI. I'll just have to write my own SCSI core.
> _We_ together can do this in parallel to the old SCSI Core.
>
> This is the whole idea.
The question is: Who starts and leads seriously this effort (and takes
in the course others with him)?
Just telling others where to go and waiting until they carry you there
usually doesn't succeed if you are not the boss of them (and/or they
are free to leave at any time without significant punishment).
> > makes sense (and you - as the maintainer - accept their patches). And in
[...]
> > a few years the "old" SCSI core fades out as legacy drives fade out (or
> > they will happily coexist forever).
>
> Yep, I've been saying this since 2002. On the linux-scsi ML.
Perhaps speaking is not enough and work should follow?
All people who really do the work like those others standing beneath
(possibly doing their own thing) and telling them how to do their own
work best.
> And this is the problem: *you* and "the community" see things in
> *this* way: "your balls - my balls", "yours/mine".
It's at most (and actually exactly) "my work - your work", not "my balls
- your balls" (or "code" or whatever).
If you want to play "our work" (read: team[0] work), than you have to
cope with others (and they with you), their - probably historically
grown - design (even if it is wrong), etc.
If this doesn't work (and ATM I have this impression) for whatever
reason, the second step is "my work, your work".
And if two (or more) people have different design opinions (and
different opinions about "quality" and/or "correct vs wrong" - I can't
decide since I have virtually no knowledge about SCSI core internals,
discussions on the Linux-SCSI-ML, etc. to decide - not even for me -,
who is "right" and/or "wrong" in which aspect or in general), it comes
down to "better the not-so-good design and working code than the best
design and no code".
So just copy the old core, throw out what you don't want, need and/or
like and voila. If it *is* "better", it will succeed and people will
come and help.
Of course it is probably more work in the short and in the long run to
maintain a separate block driver for SAS storage, but it is at least a
possible solution.
Perhaps all relevant people will see that the difference is small enough
to converge to some point in between.
Bernd
[0]: Not in the ironic interpretation in German which translates roughly
to "great, another one does it".
--
Firmix Software GmbH http://www.firmix.at/
mobil: +43 664 4416156 fax: +43 1 7890849-55
Embedded Linux Development and Services
Arjan van de Ven wrote:
> On Thu, 2005-09-29 at 06:04 +0200, Willy Tarreau wrote:
>>On Wed, Sep 28, 2005 at 07:04:31PM -0400, Jeff Garzik wrote:
>>
>>>Linux is about getting things done, not being religious about
>>>specifications. You are way too focused on the SCSI specs, and missing
>>>the path we need to take to achieve additional flexibility.
AFAIU, demands to get our concepts closer to SAM concepts are actually
motivated by this: To achieve additional flexibility. (In particular, to
ease integration of the various transports.)
>>>With Linux, it's all about evolution and the path we take.
>>
>>Hmmm... I'm fine with "not being religious about specs", but I hope we
>>try to respect them as much as possible
>
> a spec describes how the hw works... how we do the sw piece is up to
> us ;)
We implement drivers of initiators. (Well, targets too.) The specs
describe _what_ initiators do. Thereby they partly describe _how_
drivers of initiators (our sw pieces) work.
> (I know the scsi stuff also provides sort of a reference "here is how
> you can do it in sw" but I see that more as you "you need this
> functionality" not "you need this exact architecture in your software")
This is correct. The SAM is what it is --- the SCSI-3 Architecture
Model, not the architecture model of Linux' SCSI stack.
However it is very desirable to reflect layers and concepts of the SAM
in our stack. One class of reasons is maintainability. No person is able
to understand the stack; nor is a person able to consume and understand
all or even half of the SCSI specs. No person is able to construct a
mapping between the whole stack and the whole SCSI-3 Architecture Model
(in his mind or with pencil and paper...). Therefore there have to be
_components_ of the stack's architecture model which map 1:1 to
_components_ of the SCSI-3 Architecture Model.
Fortunately, SAM layers and concepts are already there in the stack,
although incomplete and incoherent. It will always be disputable _how_
complete and coherent our software should be in this respect. However it
is out of a question that our software's architecture model might
arbitrarily differ from the SAM.
--
Stefan Richter
-=====-=-=-= =--= ===-=
http://arcgraph.de/sr/
Stefan Richter wrote:
> Arjan van de Ven wrote:
>
>> On Thu, 2005-09-29 at 06:04 +0200, Willy Tarreau wrote:
>>
>>> On Wed, Sep 28, 2005 at 07:04:31PM -0400, Jeff Garzik wrote:
>>>
>>>> Linux is about getting things done, not being religious about
>>>> specifications. You are way too focused on the SCSI specs, and
>>>> missing the path we need to take to achieve additional flexibility.
>
>
> AFAIU, demands to get our concepts closer to SAM concepts are actually
> motivated by this: To achieve additional flexibility. (In particular, to
> ease integration of the various transports.)
That's what transport classes help achieve.
We just gotta move gunk from the core (HCIL etc.) to scsi_transport_spi
before we get there.
> We implement drivers of initiators. (Well, targets too.) The specs
> describe _what_ initiators do. Thereby they partly describe _how_
> drivers of initiators (our sw pieces) work.
Mostly agreed. Some of the firmware-based and emulated SCSI stuff is a
bit of an I_T mix.
> However it is very desirable to reflect layers and concepts of the SAM
> in our stack. One class of reasons is maintainability. No person is able
> to understand the stack; nor is a person able to consume and understand
> all or even half of the SCSI specs. No person is able to construct a
> mapping between the whole stack and the whole SCSI-3 Architecture Model
> (in his mind or with pencil and paper...). Therefore there have to be
> _components_ of the stack's architecture model which map 1:1 to
> _components_ of the SCSI-3 Architecture Model.
>
> Fortunately, SAM layers and concepts are already there in the stack,
> although incomplete and incoherent. It will always be disputable _how_
> complete and coherent our software should be in this respect. However it
> is out of a question that our software's architecture model might
> arbitrarily differ from the SAM.
I think just about everybody agrees with this.
The current thread is more about the path to take, to get there...
The general point about specs is that you gotta think about them, not
just blindly implement them. SNIA for example is notorious for
generating silly storage-related specifications. And some of the T10
stuff is... well... obviously designed by committee :)
Jeff
Luben,
I'd really prefer if you'd just stop on your tirade and just send in a
10 line patch for the existing linux SCSI subsystem to fix something
you think is wrong.
Code talks, bullshit walks.
Sure, Linux SCSI might not be ideal, but how many people do you know
have SAS storage on their home PCs right now? Heck, I don't have SATA
or PIV on my home system!
And as a customer of Adaptec hardware, I'm getting to the point of
seriously taking my money and going elsewhere for my storage needs.
If you are a general example of how Adaptec works with its customers,
then I want nothing to do with you or your products.
Sure, I know you think Linux is stuck in the past, so help us move to
the future in small baby steps. It doesn't require big huge leaps
like you're proposing. I mean, have you actually tried to your old
legacy SCSI controllers in a system with your new hardware? How did
your testing go?
Now I'm not a programmer, and I can't talk like one, but in my real
life job I'm a SysAdmin and knowing what I know about Adaptec's
interactions on this list will certainly color my perceptions of your
hardware and trying to make it work with my company.
John
On Thu, 29 Sep 2005 12:58:16 EDT, Luben Tuikov wrote:
> On 09/29/05 12:56, Jeff Garzik wrote:
> > Luben Tuikov wrote:
> >
> >>On 09/29/05 11:17, Bernd Petrovitsch wrote:
> >>
> >>
> >>>Then submit your driver as a (separate) block device in parallel to the
> >>>existing SCSI subsystem. People will use it for/with other parts if it
> >>
> >>
> >>SAS is ultimately SCSI. I'll just have to write my own SCSI core.
> >>_We_ together can do this in parallel to the old SCSI Core.
> >
> >
> > You should have stated this plainly, from the start.
> >
> > If you want to do your own SCSI layer, you need to do it at the block
> > layer rather than poking around drivers/scsi/
>
> So now you are saying that I should _not_ poke at drivers/scsi?
> (as I haven't done)
>
> Are you going to make up your mind?
Luben, I think you are missing the distinction being made here and that
distinction is very important.
It is *critical* to hardware vendors, to the linux community, and even
at this point to some of your competitors in the HBA space that we find
the best solutions that work well for *everyone*. The more often we
wind up with independent, unique stacks and unrelated methods and
mechanisms in the kernel, the more work we all have to do to support
Linux. If every HBA out there that thought there were following a new
and interesting technology and were going to code to the perfect ISO
or T10 or IETF layering model, the linux kernel would be one huge,
inconsistent, bloated stinking mess for the rest of us to support.
Worse, all of our customers would see different behaviors in semantics,
functionality, and support matrices for every HBA, hardware component,
or combination of platform/HBA/storage subsystem.
I believe that for you personally to find success in the Linux development
community (much as you probably do in the standards or HBA community)
is that you have to talk off your personal hat, you have to take off
your employer's hat, and you must put on the Linux community hat for
a while and see through their eyes.
In this case, Jeff and others are providing two options with a common
goal. The common goal is to increase the overall amount of commonality
and common code in Linux in this case.
You can do that two ways: Start with a new SCSI core library and show
with code how it works for multiple HBA vendors (this includes working
with your competitors!) OR help to evolve the current code to better
address your needs while not breaking the needs of other consumers.
Either approach is valid. You can start sending patches to update the
SCSI core code to simplify your driver and fit with the current
community model, OR you can put forward not just a model but the
libraries and proof-of-concepts (possibly while working with other
HBA vendors) in the form of Linux kernel code to demonstrate the
viability of a new stack which satisfies the wider community goals of
ease of maintainence and ease of understanding over time.
In general, if you think you see a contraction coming from the community,
I'd encourage you to look more closely - there are some strong guiding
principles for the community.
I suggest reading through a few of these resources which might help:
http://lists.osdl.org/pipermail/os_drivers/attachments/20050426/261c7d9d/DeviceDriverDevelopmentPlan-v.02-0001.pdf
http://www.madrone.org/mentor/linux-mentoring.pdf
I'm sure others have simmilar materials floating around. You are not
the first person to suffer from culture shock here but the sooner you
understand the goals of the community and show how to help meet those
goals (hopefully with code to substantiate your goals, and the ability
to incorporate feedback and give feedback) the sooner we'll have a working
driver in mainline.
gerrit
On 09/29/05 12:54, Jeff Garzik wrote:
> Luben Tuikov wrote:
>
>>of SAS. THE REASON THEY WERE INTRODUCED INTO LINUX BY JB IS TO
>>ACCOMODATE MPT-based SOLUTIONS FROM TWIDDLING WITH IOCTLS!
>
>
> Wrong. This shows you fundamentally don't understand transport classes
> at all.
>
> AFAIK, the first transport class was FC, for qla2xxx.
>
> Read the code to see how FC avoids the SPI-centric scan -- an example of
> transport independence.
And it shows that you do not understand SAM.
How do I know this: simple: JB's "transport attributes" have
NOTHING to do with SAM.
They break the layering architecture for one, and are
ATTRIBUTE EXPORTING FACILITY for another.
I understand that you want to preserve your friend's
bal^w^w^wpride but, lets face it:
I do not try to shove my solution down JB's throat.
As I've said many times: they are different due to
the *technology they represent*, which differs in
implmentation, and they can coexist!
If you can say this statement:
"The core problem is that a SAM-friendly path to SAS
has already been chosen -- transport classes -- and
your driver isn't following this path."
This means that you have NO CLUE ABOUT SAS or SAM!
I certainly hope that things would improve once you
start reading specs and talking to the engineers
who designed BCM8603. (If you are still going to
write their driver for them.)
>>How do I know this: simple: JB's "transport attributes" have
>>NOTHING to do with SAM.
>>
>>They break the layering architecture for one, and are
>>ATTRIBUTE EXPORTING FACILITY for another.
>
>
> Transport class == transport layer. Eventually this will sink in.
>
> Transport class allows for complete transport independence, be it SAS,
> FC, iSCSI, or other.
Nah -- all FUD.
See how you're talking general stuff. See how I talk
specifics:
The host template was introduced to satisfy SPI only
LLDD which was everything available at that time and
SAM didn't exist yet.
Over time it was enlarged to accomodate others and
all LLDD implemented it and simulated SPI centric
view.
Now, you have a storage chip on a pci device which is
NOT a host template material.
I.e. the LLDD is a _PCI_ device driver, NOT SCSI!
It exports only a SAM section 5, 6 and 7 view of
the Service Delivery Subsystem and interconnect.
It does _not_ export anything "scsi host" like.
For this reason you _need_ a management layer
on top, but _below_ SCSI Core, since that management
layer is _transport_ specific _and_ SCSI Core
should be completely _unaware_ of the transport!
Then _this_ transport layer, presents things
to the SCSI Core as "scsi host" material.
Among the many, lets take for example this
member of the struct scsi_host_template
along with the comment:
/*
* In many instances, especially where disconnect / reconnect are
* supported, our host also has an ID on the SCSI bus. If this is
* the case, then it must be reserved. Please set this_id to -1 if
* your setup is in single initiator mode, and the host lacks an
* ID.
*/
int this_id;
SPI-centric?
How about this from scsi_host:
/*
* These three parameters can be used to allow for wide scsi,
* and for host adapters that support multiple busses
* The first two should be set to 1 more than the actual max id
* or lun (i.e. 8 for normal systems).
*/
unsigned int max_id;
unsigned int max_lun;
unsigned int max_channel;
And I can continue to give examples of this for as many lines
are in the header files of Linux SCSI.
Now Jeff will say: "Then submit patches to fix this."
> I'm merely stating I'm submitting patches to clean up SCSI core. Others
> have submitted far more patches than I. And further patches to SCSI
I've also submitted patches to improve SCSI Core. Those improvements
came directly from my own mini-SCSI Core implementation of iSCSI Target.
For example, using the slab cache for scsi commands.
Thanks to Doug L, and Andi K, they made it in, if it had been left
to James Bottomley, they'd never be in.
Then I continued to post RFCs and various other suggestions, like
64 bit LUN, elimination of HCIL -- all shot down by your friends
in the community.
This was back when you had just started working on libata.
So please spare me the political sap -- I've tears in my eyes already.
> core are needed to properly integrate SAS as a transport completely
Stop this FUD man -- it integrates right now:
http://linux.adaptec.com/sas/
> independent from SPI. I'm going to be putting time and effort into
> moving the SCSI core away from SPI, so that SAS can be properly integrated.
So you are going to give all currently existsing legacy LLDD
a heart attack?
Or are you going to create new functionality as I had
outlined here:
http://marc.theaimsgroup.com/?l=linux-scsi&m=112794008820004&w=2
You know, "struct scsi_domain_device", proper LU
scannint, etc.
> All I've seen from you is
> (a) complaints that the SCSI core is too SPI-centric
I've been wanting to change this since 2003. I
even wrote an email that I wanted to completely
rewrite SCSI Core for 2.7 in 2003. See this email.
http://marc.theaimsgroup.com/?l=linux-scsi&m=104508658212335&w=2
Sadly as most discussions in linux-scsi nothing materializes,
patches get dropped, etc, etc, et.
> (b) a solution that does nothing to fix this
But it gets you one step closed to it. It merges _cleanly_,
people can use it get comfortable with it and eventually
things else where would improve as people get comfortable
with it.
> My goal is Linux. Always has been. I put quality of Linux code, and
> giving features to Linux users, above all else. Have been doing so
> regardless of who employs me, for many years now.
>
> Maybe one day I will be independently wealthy, be a completely
> independent Linux maintainer, and then people will have to find
Jeff, if you think that if one day if you became independently
wealthy you'd be an independent Linux maintainer, or
do _any_ kind of work, you need to mature a bit more.
I _guarantee_ you that in 5 years you'd think differently.
Independently wealthy people start doing charity work
and then they use that to get into politics, in order
to obtain that which lacks from just having a ton of money:
power.
Luben
> something other than Red Hat as the reason for why their code is
> receiving criticism.
>
>
>
>>I doubt you've ever been honest with me.* The reason is that
>>you are trying to push down my throat JB's "transport classes",
>>all the while you're saying I'm supposed to change other people's
>>code?
>
>
> To get a fully SPI-independent SCSI core, we must change other people's
> code. That's the way Linux works. We evolve the existing code.
>
> Jeff
>
>
>
On 09/29/05 13:13, Bernd Petrovitsch wrote:
> different opinions about "quality" and/or "correct vs wrong" - I can't
> decide since I have virtually no knowledge about SCSI core internals,
Ok.
> discussions on the Linux-SCSI-ML, etc. to decide - not even for me -,
> who is "right" and/or "wrong" in which aspect or in general), it comes
> down to "better the not-so-good design and working code than the best
> design and no code".
That sounds very fine, _but_ "the community" isn't a "corporation".
"The community" is by far and wide very close friends, so if you
point out to one of them that his code is wrong, even if all
other see that you're indeed correct, no one would say anything.
Why? Because he doesn't want to same thing done to him.
So it doesn't matter who is right or who is wrong. What matters
is who has political power to have it his way.
> So just copy the old core, throw out what you don't want, need and/or
> like and voila. If it *is* "better", it will succeed and people will
> come and help.
Blesses art thou, who believeth.
I wish it worked like this, I really wished. Sadly its doesn'
work like this.
James is a strong political figure. He keeps people who he thinks
know more than him at bay. I can quote several names here, who
are active and some who were active at one point or another,
all very well versed in the T10 ways, but it wouldn't be fare to them.
So what you have is a strong political game: they don't care
what is right or wrong, they'll implement it the way _they_ think
is right, in effect alongside _their_ code.
I'm not sure how much History the readers have studied, but such
politics have always yielded to extinction.
The reason is _not_ because you reject something, but because
you end up always doing it always _your_ way. Eventually you
become unfit to compete when the world has changed _so much_
around you, that "your way" is no longer relevant and the change
to make you fit is so radical, that it is impossible to do.
So you see, it is _not_ about accepting code, it is about
accepting _ideas_ and _innovation_.
James can still do everything _his_ way. The question is
how many _years_ would this be relevant?
> [0]: Not in the ironic interpretation in German which translates roughly
> to "great, another one does it".
Yes, but in "the community" people want "great, he does it _my_ way".
Luben
Luben Tuikov wrote:
> On 09/28/05 18:43, Andre Hedrick wrote:
>>Have you and company considered the approach of mapping to a library of
>>sorts?
>
> Hmm, it is not a library.
>
> It is a layer, again, because of what the chip actually is, and because
> of what it implements.
>
> Take a look at the announcement text, I do give some description there
> and in the code the drivers/scsi/sas-class/README file describes
> the event/managment infrastructure. Also you can take a look at the code.
> http://linux.adaptec.com/sas/
>
> What you'll see in the code is:
>
> hardware implementation (interconnect, SAM 4.15, 1.3)
> firmware implementation (interconnect, SDS, SAM 4.6, 1.3)
> LLDD (SAM, section 5, 6, 7)
> Transport Layer (SAM 4.15, SAS)
> SCSI Core (SAM section 4,5,8)
> Commmand Sets (SAM section 1)
>
> A very nice explanation in latest SAM4r03,
> section 4.15 The SCSI model for distributed communications.
BTW, Linux' implementations of transports like USB storage and SBP-2
have always been similarly layered. (Actually they come with at least
one more layer between LLDD and SCSI core.) Needless to say that these
transports need their specific managing infrastructures. So this
layering is not at all new to Linux.
> Now for MPT based solutions you have:
>
> LLDD (SAM, section 5, 6, 7)
> SCSI Core (SAM section 4,5,8)
> Commmand Sets (SAM section 1)
>
> You see? No Transport Layer between LLDD and SCSI Core!
> Why? Because all this work is done in FIRMWARE!
--
Stefan Richter
-=====-=-=-= =--= ===-=
http://arcgraph.de/sr/
Well said John!
For that matter get us a driver for the embedded 7902 (is that the one?
I forget now) with host raid support.
John Stoffel wrote:
> Luben,
>
> I'd really prefer if you'd just stop on your tirade and just send in a
> 10 line patch for the existing linux SCSI subsystem to fix something
> you think is wrong.
>
> Code talks, bullshit walks.
>
> Sure, Linux SCSI might not be ideal, but how many people do you know
> have SAS storage on their home PCs right now? Heck, I don't have SATA
> or PIV on my home system!
>
> And as a customer of Adaptec hardware, I'm getting to the point of
> seriously taking my money and going elsewhere for my storage needs.
> If you are a general example of how Adaptec works with its customers,
> then I want nothing to do with you or your products.
>
> Sure, I know you think Linux is stuck in the past, so help us move to
> the future in small baby steps. It doesn't require big huge leaps
> like you're proposing. I mean, have you actually tried to your old
> legacy SCSI controllers in a system with your new hardware? How did
> your testing go?
>
> Now I'm not a programmer, and I can't talk like one, but in my real
> life job I'm a SysAdmin and knowing what I know about Adaptec's
> interactions on this list will certainly color my perceptions of your
> hardware and trying to make it work with my company.
>
> John
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
Jeff Garzik wrote:
> * Avoids (rather than fix) several SCSI core false dependencies on HCIL.
BTW, other SCSI transport layers in Linux do this too, and have been
doing so for some time. So this is hardly a valid reason not to include
the new SAS layer.
--
Stefan Richter
-=====-=-=-= =--= ===-=
http://arcgraph.de/sr/
Jeff Garzik wrote:
>> The sad truth is that SCSI Core knows only HCIL.
>
> That's something that needs fixing, for SAS.
Not just for SAS.
>> The code doesn't alter Linux SCSI or anyone else's behaviour.
>> It only _provides_ SAS support to the kernel.
>
> That's one of the problems: It should update the SCSI core.
Sure, but the same is true for the other transports except for SPI.
--
Stefan Richter
-=====-=-=-= =--= ===-=
http://arcgraph.de/sr/
On Thu, Sep 29, 2005 at 09:44:08AM +0200, Arjan van de Ven wrote:
> On Thu, 2005-09-29 at 06:04 +0200, Willy Tarreau wrote:
> > On Wed, Sep 28, 2005 at 07:04:31PM -0400, Jeff Garzik wrote:
> > > Linux is about getting things done, not being religious about
> > > specifications. You are way too focused on the SCSI specs, and missing
> > > the path we need to take to achieve additional flexibility.
> > >
> > > With Linux, it's all about evolution and the path we take.
> >
> > Hmmm... I'm fine with "not being religious about specs", but I hope we
> > try to respect them as much as possible
>
> a spec describes how the hw works... how we do the sw piece is up to
> us ;)
No Arjan, you cannot say that ! (well, of course you can but in this case
you may be wrong). A spec describes any process, whether it's soft or hard,
and BTW, the frontier between soft and hard is diminishing. When I designed
a PI-Bus-PCI bridge 10 years ago, I used PCI 2.1 Specification. And it was
more related to software than hardware (FSMs, config registers, etc...).
It's the *implementation* which is up to us, not the spec. A spec will never
tell you that you have to be compliant with 4k stacks or things like this.
This is implementation. What it tells you is when interrupt X strikes and
you read bit Y from reg Z, then you must reset bit Y before leaving. And this
is software specs, not hardware.
> (I know the scsi stuff also provides sort of a reference "here is how
> you can do it in sw" but I see that more as you "you need this
> functionality" not "you need this exact architecture in your software")
Keeping close to an accepted standard model makes it far easier to upgrade
later, but you're right, the spec does not tell you what your implementation
must look like.
I think we agree but just don't give the exact same meaning to words.
Regards,
Willy
Jeff Garzik wrote:
[...]
> HCIL stuff to move to SPI-specific transport code.
>
> That is the task that must be completed BEFORE transport layer for SAS
> can be fully merged.
So it could at least be _halfway_ merged, like it was done with the
other non-SPI transport layers long ago, couldn't it?
--
Stefan Richter
-=====-=-=-= =--= ===-=
http://arcgraph.de/sr/
On Thu, 29 Sep 2005, Arjan van de Ven wrote:
>
> a spec describes how the hw works... how we do the sw piece is up to
> us ;)
How we do the SW is indeed up to us, but I want to step in on your first
point.
Again.
A "spec" is close to useless. I have _never_ seen a spec that was both big
enough to be useful _and_ accurate.
And I have seen _lots_ of total crap work that was based on specs. It's
_the_ single worst way to write software, because it by definition means
that the software was written to match theory, not reality.
So there's two MAJOR reasons to avoid specs:
- they're dangerously wrong. Reality is different, and anybody who thinks
specs matter over reality should get out of kernel programming NOW.
When reality and specs clash, the spec has zero meaning. Zilch. Nada.
None.
It's like real science: if you have a theory that doesn't match
experiments, it doesn't matter _how_ much you like that theory. It's
wrong. You can use it as an approximation, but you MUST keep in mind
that it's an approximation.
- specs have an inevitably tendency to try to introduce abstractions
levels and wording and documentation policies that make sense for a
written spec. Trying to implement actual code off the spec leads to the
code looking and working like CRAP.
The classic example of this is the OSI network model protocols. Classic
spec-design, which had absolutely _zero_ relevance for the real world.
We still talk about the seven layers model, because it's a convenient
model for _discussion_, but that has absolutely zero to do with any
real-life software engineering. In other words, it's a way to _talk_
about things, not to implement them.
And that's important. Specs are a basis for _talking_about_ things. But
they are _not_ a basis for implementing software.
So please don't bother talking about specs. Real standards grow up
_despite_ specs, not thanks to them.
Linus
--- Stefan Richter <[email protected]> wrote:
> Luben Tuikov wrote:
> > What you'll see in the code is:
> >
> > hardware implementation (interconnect, SAM 4.15, 1.3)
> > firmware implementation (interconnect, SDS, SAM 4.6, 1.3)
> > LLDD (SAM, section 5, 6, 7)
> > Transport Layer (SAM 4.15, SAS)
> > SCSI Core (SAM section 4,5,8)
> > Commmand Sets (SAM section 1)
> >
> > A very nice explanation in latest SAM4r03,
> > section 4.15 The SCSI model for distributed communications.
>
> BTW, Linux' implementations of transports like USB storage and SBP-2
> have always been similarly layered. (Actually they come with at least
> one more layer between LLDD and SCSI core.) Needless to say that these
> transports need their specific managing infrastructures. So this
> layering is not at all new to Linux.
True, true.
But those subsystems are shielded from SCSI Core. Plus SCSI Core
is managed by people unaware of SAM or the layering infrastructure.
Luben
> > Now for MPT based solutions you have:
> >
> > LLDD (SAM, section 5, 6, 7)
> > SCSI Core (SAM section 4,5,8)
> > Commmand Sets (SAM section 1)
> >
> > You see? No Transport Layer between LLDD and SCSI Core!
> > Why? Because all this work is done in FIRMWARE!
>
> --
> Stefan Richter
> -=====-=-=-= =--= ===-=
> http://arcgraph.de/sr/
>
On Thu, Sep 29, 2005 at 02:39:44PM -0400, Luben Tuikov wrote:
> So you see, it is _not_ about accepting code, it is about
> accepting _ideas_ and _innovation_.
>
> James can still do everything _his_ way. The question is
> how many _years_ would this be relevant?
Is your cat sleeping on your underscore key?
Joel
--
"There is no more evil thing on earth than race prejudice, none at
all. I write deliberately -- it is the worst single thing in life
now. It justifies and holds together more baseness, cruelty and
abomination than any other sort of error in the world."
- H. G. Wells
Joel Becker
Principal Software Developer
Oracle
E-mail: [email protected]
Phone: (650) 506-8127
<fun_but_off_topic>
[Removing most of the CC. Because they've got real work to do]
On 9/29/05, Linus Torvalds <[email protected]> wrote:
>
[...]
> A "spec" is close to useless.
The only usefulness of a spec is to allow to differ between morons and assholes.
http://diveintomark.org/archives/2004/08/16/specs
Couldn't resist.
</fun_but_off_topic>
J
--- Linus Torvalds <[email protected]> wrote:
>
> A "spec" is close to useless. I have _never_ seen a spec that was both big
> enough to be useful _and_ accurate.
>
> And I have seen _lots_ of total crap work that was based on specs. It's
> _the_ single worst way to write software, because it by definition means
> that the software was written to match theory, not reality.
A spec defines how a protocol works and behaves. All SCSI specs
are currently very layered and defined by FSMs.
This is _the reason_ I can plug in an Adaptec SAS host adapter
to Vitesse Expander which has a Seagate SAS disk attached to phy X...
And guess what? They interoperate and communicate with each other.
Why? Because at each layer (physical/link/phy/etc) each
one of them follow the FSMs defined in the, guess where, SAS spec.
If you take a SAS/SATA/FC/etc course, they _show you_ a link
trace and then _show_ you how all of it is defined by the FSM
specs, and make you follow the FSMs.
> So there's two MAJOR reasons to avoid specs:
Ok, then I accept that you and James Bottomley and Christoph are
_right_, and I'm wrong.
I see we differ in ideology.
> It's like real science: if you have a theory that doesn't match
> experiments, it doesn't matter _how_ much you like that theory. It's
> wrong. You can use it as an approximation, but you MUST keep in mind
> that it's an approximation.
But this is _the_ definition of a theory. No one is arguing that
a theory is not an approximation to observed behaviour.
What you have here is interoperability. Only possible because
different vendors follow the same spec(s).
> - specs have an inevitably tendency to try to introduce abstractions
> levels and wording and documentation policies that make sense for a
> written spec. Trying to implement actual code off the spec leads to the
> code looking and working like CRAP.
Ok, I give up: I'm wrong and you and James B are right.
> The classic example of this is the OSI network model protocols. Classic
Yes, it is a _classic_ example and OSI is _very_ old.
_But_ the tendency of representing things in a _layered_, object oriented
design has persisted.
> spec-design, which had absolutely _zero_ relevance for the real world.
> We still talk about the seven layers model, because it's a convenient
> model for _discussion_, but that has absolutely zero to do with any
> real-life software engineering. In other words, it's a way to _talk_
> about things, not to implement them.
Ok.
> And that's important. Specs are a basis for _talking_about_ things. But
> they are _not_ a basis for implementing software.
Ok. Let's forget about maintenance and adding _new_ functionality.
> So please don't bother talking about specs. Real standards grow up
> _despite_ specs, not thanks to them.
Yes, you're right. Linus is always right.
Now to things more pertinent, which I'm sure people are interested in:
Jeff has been appointed to the role of integrating the SAS code
with the Linux SCSI _model_, with James Bottomley's "transport attributes".
So you can expect more patches from him.
Regards,
Luben
P.S. I have to get this 8139too.c network card here working.
Luben,
The role of standard bodies is to primarily enforce interoperability but
while they suggest FSMs and layering, those directives are not mandatory.
I have also seen industrial SCSI Core implementations from various sources
to come to the following conclusions (i) they do not implement all the
manadatory stuff (ii) they implement just enough to get by with
interoperability [who has the time] (iii) any layering design is
evolutionary and (iv) none of them come close to the T10 FSMs.
You may disagree, but there needs to be a balance between standards and
implementations.
Luben Tuikov
<[email protected]
m> To
Sent by: Linus Torvalds <[email protected]>,
linux-scsi-owner@ Arjan van de Ven
vger.kernel.org <[email protected]>
cc
Willy Tarreau <[email protected]>,
09/29/2005 04:20 SCSI Mailing List
PM <[email protected]>,
Andrew Morton <[email protected]>,
Linux Kernel Mailing List
Please respond to <[email protected]>,
[email protected] Luben Tuikov
<[email protected]>, Jeff
Garzik <[email protected]>
Subject
Re: I request inclusion of SAS
Transport Layer and AIC-94xx into
the kernel
--- Linus Torvalds <[email protected]> wrote:
>
> A "spec" is close to useless. I have _never_ seen a spec that was both
big
> enough to be useful _and_ accurate.
>
> And I have seen _lots_ of total crap work that was based on specs. It's
> _the_ single worst way to write software, because it by definition means
> that the software was written to match theory, not reality.
A spec defines how a protocol works and behaves. All SCSI specs
are currently very layered and defined by FSMs.
This is _the reason_ I can plug in an Adaptec SAS host adapter
to Vitesse Expander which has a Seagate SAS disk attached to phy X...
And guess what? They interoperate and communicate with each other.
Why? Because at each layer (physical/link/phy/etc) each
one of them follow the FSMs defined in the, guess where, SAS spec.
If you take a SAS/SATA/FC/etc course, they _show you_ a link
trace and then _show_ you how all of it is defined by the FSM
specs, and make you follow the FSMs.
> So there's two MAJOR reasons to avoid specs:
Ok, then I accept that you and James Bottomley and Christoph are
_right_, and I'm wrong.
I see we differ in ideology.
> It's like real science: if you have a theory that doesn't match
> experiments, it doesn't matter _how_ much you like that theory. It's
> wrong. You can use it as an approximation, but you MUST keep in mind
> that it's an approximation.
But this is _the_ definition of a theory. No one is arguing that
a theory is not an approximation to observed behaviour.
What you have here is interoperability. Only possible because
different vendors follow the same spec(s).
> - specs have an inevitably tendency to try to introduce abstractions
> levels and wording and documentation policies that make sense for a
> written spec. Trying to implement actual code off the spec leads to
the
> code looking and working like CRAP.
Ok, I give up: I'm wrong and you and James B are right.
> The classic example of this is the OSI network model protocols.
Classic
Yes, it is a _classic_ example and OSI is _very_ old.
_But_ the tendency of representing things in a _layered_, object oriented
design has persisted.
> spec-design, which had absolutely _zero_ relevance for the real world.
> We still talk about the seven layers model, because it's a convenient
> model for _discussion_, but that has absolutely zero to do with any
> real-life software engineering. In other words, it's a way to _talk_
> about things, not to implement them.
Ok.
> And that's important. Specs are a basis for _talking_about_ things.
But
> they are _not_ a basis for implementing software.
Ok. Let's forget about maintenance and adding _new_ functionality.
> So please don't bother talking about specs. Real standards grow up
> _despite_ specs, not thanks to them.
Yes, you're right. Linus is always right.
Now to things more pertinent, which I'm sure people are interested in:
Jeff has been appointed to the role of integrating the SAS code
with the Linux SCSI _model_, with James Bottomley's "transport attributes".
So you can expect more patches from him.
Regards,
Luben
P.S. I have to get this 8139too.c network card here working.
On Thu, 29 Sep 2005, Luben Tuikov wrote:
>
> > It's like real science: if you have a theory that doesn't match
> > experiments, it doesn't matter _how_ much you like that theory. It's
> > wrong. You can use it as an approximation, but you MUST keep in mind
> > that it's an approximation.
>
> But this is _the_ definition of a theory. No one is arguing that
> a theory is not an approximation to observed behaviour.
No.
A scientific theory is an approximation of observed behaviour WITH NO
KNOWN HOLES.
Once there are known holes in the theory, it's not a scientific theory. At
best it's an approximation, but quite possibly it's just plain wrong.
And that's my point. Specs are not only almost invariably badly written,
they also never actually match reality.
At which point at _best_ it's just an approximation. At worst, it's much
worse. At worst, it causes people to ignore reality, and then it becomes
religion.
And that's way _way_ too common. People who ignore reality are sadly not
at all unusual.
"But the spec says ..." is pretty much always a sign of somebody who has
just blocked out the fact that some device doesn't.
So don't talk about specs.
Talk about working code that is _readable_ and _works_.
There's an absolutely mindbogglingly huge difference between the two.
Linus
> Once there are known holes in the theory, it's not a
> scientific theory. At best it's an approximation, but
> quite possibly it's just plain wrong.
You are right about scientific theory, but specs are not just a theory.
You are mixing "discovery" and "invention".
A scientific theory has to match reality, because the universe deveops
independently. There is no way you can enforce your theory down the
throat on the "nature".
But the roles of specs are more than that. There are two parts of it:
1. unify/summarize the reality
2. guide future implementations on a unified road
It might do job 1 poorly (simply because the reality is a mess),
but if everyone from the point on puts the effort to follow it, job 2 can
be done, and it is the real goal. It can do this simply because *humans*
can collaborate and be influenced for a goal that could eventually
benefit everybody.
> And that's my point. Specs are not only almost invariably
> badly written, they also never actually match reality.
>
> At which point at _best_ it's just an approximation. At
> worst, it's much worse. At worst, it causes people to
> ignore reality, and then it becomes religion.
Let me add more to the moron/asshole argument:
Anyone that thinks specs are reality is a moron.
Anyone that thinks specs are useless and refuses to collaborate
is an asshole. :)
On 2005-09-30, at 02:35, Linus Torvalds wrote:
>
> No.
>
> A scientific theory is an approximation of observed behaviour WITH NO
> KNOWN HOLES.
Since "approximation" is equivalent to a "known hole", there is no
single scientific theory without known holes out there?! Well that's
a segfault in brain - unless you don't consider math science of course.
A scientific theory is just a set of axioms and deduction rules. Not
much more by definition...
On Thu, Sep 29, 2005 at 04:20:13PM -0700, Luben Tuikov wrote:
>
> A spec defines how a protocol works and behaves. All SCSI specs
> are currently very layered and defined by FSMs.
A spec defines how a protocol works and behaves --- *if* it is
well-specified and unambiguous, and *if* vendors actually implement
the spec correctly. (And sometimes vendors have major economic
incentives to cheat and either intentionally violate the
specification, or simply not bother to test to make sure whether or
not they implemented their hardware correctly.)
Computing history has been literred with specifications that were
incompentently written and/or incompentently implemented --- from the
disaster known as ACPI, to FDDI (early FDDI networking gear was
interoperable only if you bought all of your gear from one vendor,
natch), consumer-grade disks which lied about when data had been
safely written to iron oxide to garner better Winbench scores, and
many, many, many others.
This is one of the reasons why the IETF doesn't bless a networking
standard until there are multiple independent, interoperable
implementations --- and even _then_ there will be edge cases that
won't be caught until much, much later.
In those cases, if you implement something which is religiously
adherent to the specification, and it doesn't interoperate with the
real world (i.e., everybody else, or some large part of the industry)
--- do you claim that you are right because you are following the
specification, and everyone else in the world is wrong? Or do you
adapt to reality? People who are too in love with specifications so
that they are not willing to be flexible will generally not be able to
achieve complete interoperability. This is the reason for the IETF
Maxim --- be conservative in what you send, liberal in what you will
accept. And it's why interoperability testing and reference
implementations are critical.
But it's also important to remember when there is a reference
implementation, or pseudo-code in the specification, it's not the only
way you can implement things. Very often, as Linus has pointed out,
there are reasons why the pseudo-code in the specification is wholely
inappropriate for a particular implementation. But that's OK; the
implementation can use a different implementastion, as long as the
result is interoperable.
Regards,
- Ted
Prasenjit,
The role of a standards body is to self promote and backslap each other
amd figure out how to divide the market and make money and not cause
problems.
The problem here is T10/T11 is the protocol is "ends justify the means".
This is where the clash of technical and design happens.
If the standards body was going to "primarily enforce interoperability",
then why the heck did the T10 proposal for "domain validation" become an
empty file and was withdrawn? IIRC it was Adaptec who helped to kill
Domain Validation on T10, but I could be wrong and correction is warrented
here if needed.
"(iv) none of them come close to the T10 FSMs" is the answer, and this
justifies Linux's position to operate under "ends justify the means".
I can tell you why the T13 proposal died. I killed when I withdrew it as
a direct result of T10's actions or lack of such.
As much as I believe in NCITS standards, they are worthless if no one is
there to assist in the process of creation, model, and adoption.
Regardless of anything stated above, the problem with creation of a scsi
standard core is most of the VOODOO of SCSI is hidden in the firmware.
James knows this fact and points it out on occassion. SCSI is a FUZZY
State Machine and nowhere close to being consider finite.
Not sure if there is a good solution to date; however, James does have an
strong understanding of the mess and Christop is a good right hand
enforcer regardless that he and I disagree more often than agree.
Cheers,
Andre Hedrick
LAD Storage Consulting Group
On Thu, 29 Sep 2005, Prasenjit Sarkar wrote:
> Luben,
>
> The role of standard bodies is to primarily enforce interoperability but
> while they suggest FSMs and layering, those directives are not mandatory.
>
> I have also seen industrial SCSI Core implementations from various sources
> to come to the following conclusions (i) they do not implement all the
> manadatory stuff (ii) they implement just enough to get by with
> interoperability [who has the time] (iii) any layering design is
> evolutionary and (iv) none of them come close to the T10 FSMs.
>
> You may disagree, but there needs to be a balance between standards and
> implementations.
>
>
>
>
>
> Luben Tuikov
> <[email protected]
> m> To
> Sent by: Linus Torvalds <[email protected]>,
> linux-scsi-owner@ Arjan van de Ven
> vger.kernel.org <[email protected]>
> cc
> Willy Tarreau <[email protected]>,
> 09/29/2005 04:20 SCSI Mailing List
> PM <[email protected]>,
> Andrew Morton <[email protected]>,
> Linux Kernel Mailing List
> Please respond to <[email protected]>,
> [email protected] Luben Tuikov
> <[email protected]>, Jeff
> Garzik <[email protected]>
> Subject
> Re: I request inclusion of SAS
> Transport Layer and AIC-94xx into
> the kernel
>
>
>
>
>
>
>
>
>
>
> --- Linus Torvalds <[email protected]> wrote:
> >
> > A "spec" is close to useless. I have _never_ seen a spec that was both
> big
> > enough to be useful _and_ accurate.
> >
> > And I have seen _lots_ of total crap work that was based on specs. It's
> > _the_ single worst way to write software, because it by definition means
> > that the software was written to match theory, not reality.
>
> A spec defines how a protocol works and behaves. All SCSI specs
> are currently very layered and defined by FSMs.
>
> This is _the reason_ I can plug in an Adaptec SAS host adapter
> to Vitesse Expander which has a Seagate SAS disk attached to phy X...
> And guess what? They interoperate and communicate with each other.
>
> Why? Because at each layer (physical/link/phy/etc) each
> one of them follow the FSMs defined in the, guess where, SAS spec.
>
> If you take a SAS/SATA/FC/etc course, they _show you_ a link
> trace and then _show_ you how all of it is defined by the FSM
> specs, and make you follow the FSMs.
>
> > So there's two MAJOR reasons to avoid specs:
>
> Ok, then I accept that you and James Bottomley and Christoph are
> _right_, and I'm wrong.
>
> I see we differ in ideology.
>
> > It's like real science: if you have a theory that doesn't match
> > experiments, it doesn't matter _how_ much you like that theory. It's
> > wrong. You can use it as an approximation, but you MUST keep in mind
> > that it's an approximation.
>
> But this is _the_ definition of a theory. No one is arguing that
> a theory is not an approximation to observed behaviour.
>
> What you have here is interoperability. Only possible because
> different vendors follow the same spec(s).
>
> > - specs have an inevitably tendency to try to introduce abstractions
> > levels and wording and documentation policies that make sense for a
> > written spec. Trying to implement actual code off the spec leads to
> the
> > code looking and working like CRAP.
>
> Ok, I give up: I'm wrong and you and James B are right.
>
> > The classic example of this is the OSI network model protocols.
> Classic
>
> Yes, it is a _classic_ example and OSI is _very_ old.
>
> _But_ the tendency of representing things in a _layered_, object oriented
> design has persisted.
>
> > spec-design, which had absolutely _zero_ relevance for the real world.
>
> > We still talk about the seven layers model, because it's a convenient
> > model for _discussion_, but that has absolutely zero to do with any
> > real-life software engineering. In other words, it's a way to _talk_
> > about things, not to implement them.
>
> Ok.
>
> > And that's important. Specs are a basis for _talking_about_ things.
> But
> > they are _not_ a basis for implementing software.
>
> Ok. Let's forget about maintenance and adding _new_ functionality.
>
> > So please don't bother talking about specs. Real standards grow up
> > _despite_ specs, not thanks to them.
>
> Yes, you're right. Linus is always right.
>
> Now to things more pertinent, which I'm sure people are interested in:
>
> Jeff has been appointed to the role of integrating the SAS code
> with the Linux SCSI _model_, with James Bottomley's "transport attributes".
> So you can expect more patches from him.
>
> Regards,
> Luben
>
> P.S. I have to get this 8139too.c network card here working.
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
Linus,
I have to tip my hat to you sir.
As much as I wanted to believe and tried to make it happen ... ATA/IDE was
forced to design many exception case events. Regardless how hard I an
others tried to invoke/create a driver to mimic the "SPEC", the hardware
people broke most of the rules and each chipset was littered with
exception cases.
It has been 7 years since you and I started butting heads, and in the end
both of us were right. A driver could be written to follow the standard
exactly, and it would never work (alone, as-is) because the hardware was
not paying attention the rules book.
Hope you can kick back and laugh about the history, too!
Have a great Day!
Andre Hedrick
LAD Storage Consulting Group
On Thu, 29 Sep 2005, Linus Torvalds wrote:
>
>
> On Thu, 29 Sep 2005, Arjan van de Ven wrote:
> >
> > a spec describes how the hw works... how we do the sw piece is up to
> > us ;)
>
> How we do the SW is indeed up to us, but I want to step in on your first
> point.
>
> Again.
>
> A "spec" is close to useless. I have _never_ seen a spec that was both big
> enough to be useful _and_ accurate.
>
> And I have seen _lots_ of total crap work that was based on specs. It's
> _the_ single worst way to write software, because it by definition means
> that the software was written to match theory, not reality.
>
> So there's two MAJOR reasons to avoid specs:
>
> - they're dangerously wrong. Reality is different, and anybody who thinks
> specs matter over reality should get out of kernel programming NOW.
> When reality and specs clash, the spec has zero meaning. Zilch. Nada.
> None.
>
> It's like real science: if you have a theory that doesn't match
> experiments, it doesn't matter _how_ much you like that theory. It's
> wrong. You can use it as an approximation, but you MUST keep in mind
> that it's an approximation.
>
> - specs have an inevitably tendency to try to introduce abstractions
> levels and wording and documentation policies that make sense for a
> written spec. Trying to implement actual code off the spec leads to the
> code looking and working like CRAP.
>
> The classic example of this is the OSI network model protocols. Classic
> spec-design, which had absolutely _zero_ relevance for the real world.
> We still talk about the seven layers model, because it's a convenient
> model for _discussion_, but that has absolutely zero to do with any
> real-life software engineering. In other words, it's a way to _talk_
> about things, not to implement them.
>
> And that's important. Specs are a basis for _talking_about_ things. But
> they are _not_ a basis for implementing software.
>
> So please don't bother talking about specs. Real standards grow up
> _despite_ specs, not thanks to them.
>
> Linus
> -
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
Linus Torvalds wrote:
>
> On Thu, 29 Sep 2005, Luben Tuikov wrote:
>
>>> It's like real science: if you have a theory that doesn't match
>>> experiments, it doesn't matter _how_ much you like that theory. It's
>>> wrong. You can use it as an approximation, but you MUST keep in mind
>>> that it's an approximation.
>>
>>But this is _the_ definition of a theory. No one is arguing that
>>a theory is not an approximation to observed behaviour.
>
>
> No.
>
> A scientific theory is an approximation of observed behaviour WITH NO
> KNOWN HOLES.
>
> Once there are known holes in the theory, it's not a scientific theory. At
> best it's an approximation, but quite possibly it's just plain wrong.
>
> And that's my point. Specs are not only almost invariably badly written,
> they also never actually match reality.
>
> At which point at _best_ it's just an approximation. At worst, it's much
> worse. At worst, it causes people to ignore reality, and then it becomes
> religion.
>
> And that's way _way_ too common. People who ignore reality are sadly not
> at all unusual.
>
> "But the spec says ..." is pretty much always a sign of somebody who has
> just blocked out the fact that some device doesn't.
>
> So don't talk about specs.
Why not?
There are good, bad and ill-timed specs. The bad ones are
ignored. Ill-timed ones gather dust, for example the
SCSI Ultra 640 standard (SPI-5) since the industry has
bet on SAS; hope they weren't expecting timely driver
support from Linux.
As for a good spec how about the Multi Media Command (MMC)
set which allows us to read music and data CDs written
almost twenty years ago plus many different formats since
then. It is currently (in MMC-5) being enhanced to cope
with the next big bun fight in that space: Blue ray and
HD-DVD (and their various content protection systems).
In the t10.org hierarchy of specs, MMC is subservient to
the primary commands (SPC) and the general architecture
(SAM). The companies that work in the MMC space (and
tend to define that standard) have "bent the rules" over
the years. The response from the (different set of)
companies that are behind SPC and SAM was to make
allowance for MMC.
The process seems to work pretty well and I am unaware
of any proposed alternate interfaces. Transports have
come and gone but the logical interface has remained.
> Talk about working code that is _readable_ and _works_.
For SAS we have a well thought out definition for what the
interface should be to hardware specific drivers IMO. It is
called CSMI, rechristened SDI. The editor of SDI is also
the editor of SAS, SAS-1.1 and SAS-2. Judging from his work,
he knows his stuff. Unfortunately SDI uses ioctls to define
its interface, which is mainly between two kernel layers
(if one ignores pass throughs). Sorry, did I mention "ioctl",
oh that makes SDI unacceptable. Almost a year ago that is what
happened to the first proposed SAS driver for Linux. That
decision has pushed Luben (amongst others) into the position
he is in now: come up with a "better" design, produce code
and then watch it get rejected. So please cut Luben a bit
of slack.
Just in case people think that I agree with Luben on using
sysfs to represent the whole SAS topology and interesting
bits suspended in it (i.e. SAS expanders), then I don't.
I am, however, prepared to argue the detail. Since the
days of Eric Youngdale I have believed that SCSI Host Bus
Adapters (HBAs) should be addressable devices, just like
network interfaces. IMO it is the block layer and its
associated end devices that are the legacy thinking.
> There's an absolutely mindbogglingly huge difference between the two.
It is ironic that as the author of the SG_IO
passthrough ioctl the "specs" that I am
often asked to help circumvent are the "we
know better" variety built into various layers
of the linux kernel :-)
Doug Gilbert
On Thu, 29 Sep 2005, David S. Miller wrote:
Dave,
Thanks for filling in the details I was missing about the TOE history.
Glad to see you laugh about the ski stuff. I thought about snowboarding
then realized I would make a great mogal for someone to do an ali off. If
you are open to questions about TOE/RDMA stuff, would like to chat with
you and see your POV on the subject.
> In that case, it is indeed a vendor trying to shove their particular
> solution down our throats. They never even attempt to try out the
> alternatives, and we've even gone through the trouble of coming up
> with several. And they do this because their whole buisness model is
> all about their scheme to the exclusion of anything else, not because
> what they have is better.
Luben,
Reading Dave's points above tends to point to adaptec's current direction,
as we all know. TOEs were rejected.
I stated I would help with SAS adoption because there is a SAS-Transport
model. I asked about a possible libadaptec + libsas, and still waiting to
see if you and adaptec are up for the task. Right now the only path open
is the one Jeff Garzik is putting forward along with James and Christop.
I have a vested interest in seeing SAS-Transport, otherwise I would have
cut and run a long time ago.
These long email threads where everyone is shout from the top of their
hill never wins anything. After a while the hill becomes flat (from all
the stomping), and you become old and tired.
LSI pointed out they mask there SAS in firmware and make it show up in a
scsi-like or scsi state. They also pointed out other vendors have taken
this road. Even if Adaptec did not go this way in hardware, there still
has to be a way to map into SCSI ... sheesh this is Adaptec known for
SCSI.
Just an FYI, would suggest you cool your heels and listen for the quiet
responses. There is more heat than light right now; maybe this thread
will offset some of the cost in the energy criss. Will pass on advice
handed to me (when I was a maintainer) relax and listen, nobody is out to
get you (and they were right).
Cheers,
Andre
PS I didn't listen to that advice back then, don't make the same mistake.
On 09/29/05 20:35, Linus Torvalds wrote:
> And that's my point. Specs are not only almost invariably badly written,
> they also never actually match reality.
Linus, the world has changed around you.
Take a look at the SAS spec and then at a SAS chip
implementation, for example.
(We're talking abou T10 specs, right?)
> And that's way _way_ too common. People who ignore reality are sadly not
> at all unusual.
You are saying I ignored reality?
> Talk about working code that is _readable_ and _works_.
http://linux.adaptec.com/sas/
Luben
On 09/30/05 03:29, Douglas Gilbert wrote:
>
> For SAS we have a well thought out definition for what the
> interface should be to hardware specific drivers IMO. It is
> called CSMI, rechristened SDI. The editor of SDI is also
> the editor of SAS, SAS-1.1 and SAS-2. Judging from his work,
> he knows his stuff. Unfortunately SDI uses ioctls to define
> its interface, which is mainly between two kernel layers
> (if one ignores pass throughs). Sorry, did I mention "ioctl",
Hi Doug,
Almost all of the SDI stuff can be extracted by a user space
library reading the SAS sysfs domain tree (which is the result
of domain discovery).
Pictures of can be found here:
http://marc.theaimsgroup.com/?l=linux-scsi&m=112629509826900&w=2
Since MPT-based hardware does domain discovery in the FIRMWARE,
this is why you do not have the domain picture as easily.
> oh that makes SDI unacceptable. Almost a year ago that is what
> happened to the first proposed SAS driver for Linux. That
> decision has pushed Luben (amongst others) into the position
> he is in now: come up with a "better" design, produce code
> and then watch it get rejected. So please cut Luben a bit
> of slack.
What James Bottomley et al. complained back then is that
"common code" to SAS should be pulled out in a "common layer".
This layer is the SAS Transport layer.
But in the mean time, LSI came out with SAS, whose driver
as you can see had nothing to do with SAS -- it was an MPT
driver after all, so James Bottomley decides that whatever
else comes along, it would use _his_ design. Whether it
works for open transport, he doesn't want to listen. He
is using his political power to enforce it.
> Just in case people think that I agree with Luben on using
> sysfs to represent the whole SAS topology and interesting
> bits suspended in it (i.e. SAS expanders), then I don't.
> I am, however, prepared to argue the detail. Since the
Sorry, since the discover process keeps an internal
representation of "what is out there" via discovery,
I just tacked a kobject to each structure I have anyway,
and showed it in sysfs.
I thought that was the whole purpose of sysfs -- to show
kernel internal structures and dependencies.
Plus, this is what it _actually_ looks in the physical world.
Also you have to admit -- it looks cool:
http://marc.theaimsgroup.com/?l=linux-scsi&m=112629509826900&w=2
> days of Eric Youngdale I have believed that SCSI Host Bus
> Adapters (HBAs) should be addressable devices, just like
> network interfaces. IMO it is the block layer and its
> associated end devices that are the legacy thinking.
Host Adapters are addressable -- if there's an initiator
on the domain, the discover process will discover it
and it will show up in the SAS sysfs tree.
> It is ironic that as the author of the SG_IO
> passthrough ioctl the "specs" that I am
> often asked to help circumvent are the "we
> know better" variety built into various layers
> of the linux kernel :-)
Indeed.
Luben
On Fri, 2005-09-30 at 17:29 +1000, Douglas Gilbert wrote:
snippage.
>
> For SAS we have a well thought out definition for what the
> interface should be to hardware specific drivers IMO. It is
> called CSMI, rechristened SDI. The editor of SDI is also
> the editor of SAS, SAS-1.1 and SAS-2. Judging from his work,
> he knows his stuff. Unfortunately SDI uses ioctls to define
> its interface, which is mainly between two kernel layers
> (if one ignores pass throughs).
I talked to one of the authors of these specs. SDI is an attempt to
create an open standard for the somewhat proprietary CSMI spec developed
by HP. It is currently languishing in t10 due to the IOCTL problem you
describe below (the "no new IOCTL's" doctrine caught them by surprise).
There is some thought to going to a write()/read() on a character device
model, but this has various problems as well.
> Sorry, did I mention "ioctl",
> oh that makes SDI unacceptable. Almost a year ago that is what
> happened to the first proposed SAS driver for Linux.
That was one of the reasons the MPT Fusion and Adaptec drivers were
rejected. There were others as well, such as lack of a SAS transport
class.
Andrew
> That
> decision has pushed Luben (amongst others) into the position
> he is in now: come up with a "better" design, produce code
> and then watch it get rejected. So please cut Luben a bit
> of slack.
>
> Just in case people think that I agree with Luben on using
> sysfs to represent the whole SAS topology and interesting
> bits suspended in it (i.e. SAS expanders), then I don't.
> I am, however, prepared to argue the detail. Since the
> days of Eric Youngdale I have believed that SCSI Host Bus
> Adapters (HBAs) should be addressable devices, just like
> network interfaces. IMO it is the block layer and its
> associated end devices that are the legacy thinking.
>
> > There's an absolutely mindbogglingly huge difference between the two.
>
> It is ironic that as the author of the SG_IO
> passthrough ioctl the "specs" that I am
> often asked to help circumvent are the "we
> know better" variety built into various layers
> of the linux kernel :-)
>
> Doug Gilbert
> -
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
On 09/30/05 12:26, Andrew Patterson wrote:
>
> I talked to one of the authors of these specs. SDI is an attempt to
> create an open standard for the somewhat proprietary CSMI spec developed
> by HP. It is currently languishing in t10 due to the IOCTL problem you
> describe below (the "no new IOCTL's" doctrine caught them by surprise).
> There is some thought to going to a write()/read() on a character device
> model, but this has various problems as well.
I think that read/write from a char device is going away too.
For this reason I showed the whole picture of the SAS
domain in sysfs _and_ created a binary file attr to
send/receive SMP requests/responses to control
the domain and get attributes ("smp_portal" binary
attr of each expander).
It is completely user space driven and a user space library
is simple to write.
See drivers/scsi/sas/expander_conf.c which is a user
space utility. For the output see Announcement 3:
http://linux.adaptec.com/sas/Announce_2.txt or here:
http://marc.theaimsgroup.com/?l=linux-scsi&m=112629509318354&w=2
The code which implements it is very tiny, at the bottom
of drivers/scsi/sas/sas_expander.c
>>Sorry, did I mention "ioctl",
>>oh that makes SDI unacceptable. Almost a year ago that is what
>>happened to the first proposed SAS driver for Linux.
>
>
> That was one of the reasons the MPT Fusion and Adaptec drivers were
> rejected. There were others as well, such as lack of a SAS transport
> class.
You mean the first Adaptec SAS "adp94xx" driver.
BTW, neither the original "adp94xx", nor the subsequent "aic94xx"
Adaptec drivers implmented _any_ ioctls for CSMI/SDI.
Luben
Luben Tuikov wrote:
> Hardware folks needs to work with software folks and
> software folks need to work with hardware folks.
>
> This is what makes good design.
This is so true, and so often overlooked when hardware is being designed
and built. A lot of it can be attributed to mismanagement and bad
communication between departments ... But, that's the drawback of the
corporate system
On 09/30/05 03:36, Andre Hedrick wrote:
> I stated I would help with SAS adoption because there is a SAS-Transport
> model. I asked about a possible libadaptec + libsas, and still waiting to
> see if you and adaptec are up for the task. Right now the only path open
> is the one Jeff Garzik is putting forward along with James and Christop.
> I have a vested interest in seeing SAS-Transport, otherwise I would have
> cut and run a long time ago.
>
> These long email threads where everyone is shout from the top of their
> hill never wins anything. After a while the hill becomes flat (from all
> the stomping), and you become old and tired.
>
> LSI pointed out they mask there SAS in firmware and make it show up in a
> scsi-like or scsi state. They also pointed out other vendors have taken
> this road. Even if Adaptec did not go this way in hardware, there still
> has to be a way to map into SCSI ... sheesh this is Adaptec known for
> SCSI.
Hi Andre,
Let me know if this 4 section write up satisfies:
Section 1: MPT, SCSI Core and JB's "transport attributes"
---------------------------------------------------------
SPI drivers (say 5 years ago)
-----------------------------
hardware implementation (bus connect)
firmware implementation (transport: SPI)
LLDD (exports SCSI devices (LUs))
SCSI Core
Command Sets
MPT-based drivers (now)
-----------------------
hardware implementation (interconnect/physical)
--> Transport Layer (firmware: FC/SPI/SAS/etc) <--
LLDD (exports SCSI devices (LUs))
SCSI Core
Command Sets
As you can see SCSI Core is _unaware_ of the transport.
The transport is completely implemented in FIRMWARE, relieving
the LLDD from worrying about it. Theoretically/ideally the same
LLDD would work for _all_ transports, since the FW would
export LUs to the LLDD, which would in turn register
those with SCSI Core.
The layout is the same as before, achieving 100% backward
software compatibility.
MPT-based drivers + James Bottomley's "transport attributes"
-------------------------------------------------------------
hardware implementation
Transport Layer <------+ FW/Transport dependent access method
LLDD <---------- + LLDD dependent access method
SCSI Core ---------------------'
Command Sets
This picture is _identical_ to the one above, but
I've also shown what the "transport attributes" achieve:
They hook to the _LLDD_ to get to LLDD dependent way of
accessing "transport attributes" (any transport). This is
JB's template unifying _all_ transports.
Note that this isn't a _management_ layer or infrastructure,
since, it _does not lie between_ the LLDD and SCSI Core.
It merely implements attribute exporting.
Section 2: USB/SBP/SAS and SCSI Core
------------------------------------
hardware implementation (interconnect/physical)
firmware implementation (SDS: TMFs + Execute Command SCSI RPC)*
LLDD (Coherent interface to SDS)
--> Transport Layer (Transport common to LLDDs) <--
SCSI Core
Command Sets
* SDS, Service Delivery Subsystem (see SAM 4.6)
TMF, Task Management Function (see SAM 7)
Execute Command SCSI RPC (see SAM 5.1)
Most immediate difference from Section 1 is that
- the Transport Layer is _above_ the LLDD (in top-down).
- no need for LLDD/Firmware dependent access method
to the Transport,
- Transport is accessed in the same way across all
LLDDs of the same transport (USB/SBP/SAS).
Now since, the LLDDs all implement TMFs + Exec Cmnd SCSI RPC,
you can have
- a transport common error handling and
- a transport common "attribute" access (sysfs),
across all LLDD of the same transport directly from userspace.
The reason the LLDDs all implement TMFs + Exec Cmnd SCSI RPC,
is that the Firmware implements it, and the reason that
the Firmware implements it is that the chip implements
it (following the transport spec).
That is, you can have _different_ LLDDs connecting you
to the _same place_ (maybe not at the same time, depending
on the transport).
SCSI Core should be completely unaware of the
Transport being used and Transport specific
Error handling is common to all such Transport
specific LLDDs (via TMFs): one for SBP, one for
USB, one for SAS.
The whole point of this USB/SBP/SAS Transport
Layering is that you can access at each level,
thus you can add new abstractions, e.g. SATL (libata),
as is shown in the SATr06 spec.
Furthermore, when you look at the USB/SBP/SAS chips
you will see nothing about "scsi_host", and all about
"transport".
And the sysfs representation of the SAS domain is analogous
to, say, the USB representation of the USB domain.
Section 3: Legacy Thinking or Thinking Legacy
---------------------------------------------
Traditionally Error Handling has been done in
SCSI Core. The reason for this is that the first
and only SCSI was Parallel SCSI and no other
SCSI was around (and that SAM didn't exist back then).
This is how we have the SPI-centric EH methods
in the scsi host template right now:
int (* eh_abort_handler)(struct scsi_cmnd *);
int (* eh_device_reset_handler)(struct scsi_cmnd *);
int (* eh_bus_reset_handler)(struct scsi_cmnd *);
int (* eh_host_reset_handler)(struct scsi_cmnd *);
This is fine for Parallel SCSI (SPI) but for other
transports it doesn't quite satisfy.
Let's admit it, with HCIL and with the EH, SCSI Core
is still very SPI centric.
But we should _not_ break legacy drivers and backward
support, yet we have to face the future.
The way we do this is we slowly, without disruption
to older drivers introduce, in parallel, emerge
a new, simpler, slimmer, faster SCSI Core, whereby
we accommodate new infrastructures, yet, have 100%
backward compatibility, via the current older
SCSI Core. After all, both would be a bunch of
functions in a bunch of files.
If X works with Y, do not disrupt it. Fix it if
it's broken. Introduce innovation, functionality,
better design, but not at the expense of breaking
legacy.
To eliminate bugs, tweak old as little as possible,
since you cannot test on _all_ hardware the old code
works on.
To achieve maximum innovation and relevance in the fast
changing world of storage, create, innovate new
better, more accommodating design and infrastructures.
Section 4: Politics
-------------------
Let's face it: SAS is a new emerging technology.
It will be the technology for the next 10-15 years,
and *everybody* in Linux SCSI wants a piece of it.
Everybody wants their name and contribution to it.
This is fine, but we need people who clearly understand
the technology and clearly understand what, how
and why it works. We need well-read and well educated
people. Linux dedication is fine, but protocol knowlege
is needed too.
Can Linux afford people who have never even read SAS
to write SAS Code for Linux. Yes, sure. It is the
Linux's ideology: "specs are cr@p".
Conclusion
----------
Even though the SAS Transport Layer follows an _already_
establised layering infrastructure for more (less?) exotic
transports such as USB and SBP, James Bottomley has resisted
its inclusion in Linux SCSI.
Have we lost our touch with the new calling it
"non-traditional"? Will Linux become a dinosaur?
I'm not sure how many times one can split the SAS code?
Will there be enough for everyone?
> Just an FYI, would suggest you cool your heels and listen for the quiet
> responses. There is more heat than light right now; maybe this thread
> will offset some of the cost in the energy criss. Will pass on advice
> handed to me (when I was a maintainer) relax and listen, nobody is out to
> get you (and they were right).
Thank you Andre for the warm advice.
James, Linus, can we have this driver in the kernel now, please?
Thank you,
Luben
On Sep 30, 2005, at 14:34:42, Luben Tuikov wrote:
> This is how we have the SPI-centric EH methods in the scsi host
> template right now:
> int (* eh_abort_handler)(struct scsi_cmnd *);
> int (* eh_device_reset_handler)(struct scsi_cmnd *);
> int (* eh_bus_reset_handler)(struct scsi_cmnd *);
> int (* eh_host_reset_handler)(struct scsi_cmnd *);
So submit patches to fix it! You clearly understand what is wrong,
so why not help change it?
> But we should _not_ break legacy drivers and backward support,
WRONG. This is not the way Linux works. We break internal APIs all
the time. If you need to change one _thats_OK_. Userspace ABI is
mostly another matter, but that's different from the internal data
structures and functions.
> The way we do this is we slowly, without disruption to older
> drivers introduce, in parallel, emerge a new, simpler, slimmer,
> faster SCSI Core, whereby we accommodate new infrastructures, yet,
> have 100% backward compatibility, via the current older SCSI Core.
> After all, both would be a bunch of functions in a bunch of files.
Except this introduces bloat and multiplies maintainer load. Fix the
existing one. If it breaks other in-core drivers, fix those to
match. If it breaks out-of-tree drivers, too bad! They should get
their code upstream and then they wouldn't need to worry.
> If X works with Y, do not disrupt it. Fix it if it's broken.
> Introduce innovation, functionality, better design, but not at the
> expense of breaking legacy.
This is not the way Linux works. It may be the way Adaptec works,
but that's not relevant here.
> Section 4: Politics
> -------------------
s/Politics.*//g; I hate politics. Keep it off this list.
Cheers,
Kyle Moffett
On 09/30/05 03:36, Andre Hedrick wrote:
> I stated I would help with SAS adoption because there is a SAS-Transport
> model. I asked about a possible libadaptec + libsas, and still waiting to
> see if you and adaptec are up for the task. Right now the only path open
> is the one Jeff Garzik is putting forward along with James and Christop.
> I have a vested interest in seeing SAS-Transport, otherwise I would have
> cut and run a long time ago.
Hi Andre,
Let me know if this satisfies:
The infrastructure is broken into
* SAS LLDD,
* SAS Layer.
The SAS LLDD does phy/OOB management, and generates SAS events
to the SAS Layer. Those events are *the only way* a SAS LLDD
communicates with the SAS Layer. If you can generate 2 types
of event, then you can use this infrastructure. The first two
are, loosely, "link was severed", "bytes were dmaed". The third
kind is "received a primitive", used for domain revalidation.
A SAS LLDD should implement the Execute Command SCSI RPC and
at least one SCSI TMF (Task Management Function), in order for
the SAS Layer to communicate with the SAS LLDD.
The SAS Layer is concerned with
* SAS Phy/Port/HA event management (LLDD generates,
SAS Layer processes),
* SAS Port management (creation/destruction),
* SAS Domain discovery and revalidation,
* SAS Domain device management,
* SCSI Host registration/deregistration,
* Device registration with SCSI Core (SAS) or libata
(SATA/PI), and
* Expander management and exporting expander control
to user space.
The SAS Layer uses the Execute Command SCSI RPC, and the TMFs
implemented by the SAS LLDD in order to manage the domain and
the domain devices.
For details please see drivers/scsi/sas/README.
The SAS Layer represents the SAS domain in sysfs. For each
object represented, its parent is the physical entity it attaches
to in the physical world. So in effect, kobject_get, gets
the whole chain up on which that object depends on.
In effect, the sysfs representation of the SAS domain(s)
is what you'd see in the physical world.
Hot plugging and hot unplugging of devices, domains and subdomains
is supported. Repeated hot plugging and hot unplugging is
also supported, naturally.
SAS introduces a new physical entity, an expander.
Expanders are _not_ SAS devices, and thus are _not_ SCSI devices.
Expanders are part of the Service Delivery Subsystem, in this case
SAS.
Expanders are controlled using the Serial Management Protocol (SMP).
Complete control is given to user space of all expanders found
in the domain, using an "smp_portal". More of this in the second
and third email in this series.
A user space program, "expander_conf.c" is also presented to show
how one controls expanders in the domain. It is located here:
drivers/scsi/sas/expanders_conf.c
Thank you,
Luben
>
> These long email threads where everyone is shout from the top of their
> hill never wins anything. After a while the hill becomes flat (from all
> the stomping), and you become old and tired.
>
> LSI pointed out they mask there SAS in firmware and make it show up in a
> scsi-like or scsi state. They also pointed out other vendors have taken
> this road. Even if Adaptec did not go this way in hardware, there still
> has to be a way to map into SCSI ... sheesh this is Adaptec known for
> SCSI.
>
> Just an FYI, would suggest you cool your heels and listen for the quiet
> responses. There is more heat than light right now; maybe this thread
> will offset some of the cost in the energy criss. Will pass on advice
> handed to me (when I was a maintainer) relax and listen, nobody is out to
> get you (and they were right).
>
> Cheers,
>
> Andre
>
> PS I didn't listen to that advice back then, don't make the same mistake.
>
>
>
On 09/30/05 14:50, Kyle Moffett wrote:
> On Sep 30, 2005, at 14:34:42, Luben Tuikov wrote:
>
>>This is how we have the SPI-centric EH methods in the scsi host
>>template right now:
>> int (* eh_abort_handler)(struct scsi_cmnd *);
>> int (* eh_device_reset_handler)(struct scsi_cmnd *);
>> int (* eh_bus_reset_handler)(struct scsi_cmnd *);
>> int (* eh_host_reset_handler)(struct scsi_cmnd *);
>
>
> So submit patches to fix it! You clearly understand what is wrong,
> so why not help change it?
Because
- I do not want to give heart attack to all existing LLDDs
- Some LLDD would never be able to be changed
- Some LLDD work on very _scarce_ hardware which we cannot test.
- plus such radical changes are neither warranted nor necessary.
It is better to keep legacy around, until all you'll have on
your new serverboard is a SAS/SATA storage chip such as
AIC-94xx or say BCM8603. Then you can compile out most
of the legacy stuff.
>>But we should _not_ break legacy drivers and backward support,
>
> WRONG. This is not the way Linux works. We break internal APIs all
> the time. If you need to change one _thats_OK_. Userspace ABI is
Well, I can never have it right. Some people say you shouldn't break
it, others say let's break the whole thing and give heart attack
to all LLDDs, other say it is impossible to change all LLDD since
the hardware is not around, etc, etc.
I think not breaking anything (for now at least) would be the
_easiest_ and most painless way to transition.
>>The way we do this is we slowly, without disruption to older
>>drivers introduce, in parallel, emerge a new, simpler, slimmer,
>>faster SCSI Core, whereby we accommodate new infrastructures, yet,
>>have 100% backward compatibility, via the current older SCSI Core.
>>After all, both would be a bunch of functions in a bunch of files.
>
>
> Except this introduces bloat and multiplies maintainer load. Fix the
> existing one. If it breaks other in-core drivers, fix those to
Well, not necessarily. It would be more painful and more maintainer
load if we did what you suggest. The overhead would be enormous.
>>Section 4: Politics
>>-------------------
>
>
> s/Politics.*//g; I hate politics. Keep it off this list.
Me too, but we are idealists. Politics is an integral part of
life.
Long time ago, in a galaxy far, far away...
I literally sat in a meeting whereby technical staff of _several_
companies agreed that Pi=3.0.
Luben
Marcin Dalecki wrote:
> On 2005-09-30, at 02:35, Linus Torvalds wrote:
>> A scientific theory is an approximation of observed behaviour WITH NO
>> KNOWN HOLES.
>
> Since "approximation" is equivalent to a "known hole", there is no
> single scientific theory without known holes out there?! Well that's a
> segfault in brain - unless you don't consider math science of course.
>
> A scientific theory is just a set of axioms and deduction rules. Not
> much more by definition...
I think a better explanation of 'scientific theory' is:
an explanation or definition of observed behaviour with no known error
which, is what I believe Linus was trying to say
[cc trimmed]
> I think a better explanation of 'scientific theory' is:
>
> an explanation or definition of observed behaviour with no known error
...that is testable. (Not that this has anything to do with the point.)
While jumping on the thread for no good reason, I might point out (to
Luben) that ^w is erase word and ^h is erase character. Your stty
settings may vary.
On Fri, 2005-09-30 at 14:34 -0400, Luben Tuikov wrote:
> James, Linus, can we have this driver in the kernel now, please?
A while ago I told you that if you could show that the transport class
abstraction could not support both the aic94xx and LSI SAS cards then we
could look at doing SAS differently. Since then you have asserted many
times that a transport class could not work for the aic94xx (mostly by
making inaccurate statements about what the transport class abstraction
is) but have never actually provided any evidence for your assertion.
In a recent prior email, you said:
> Now to things more pertinent, which I'm sure people are interested in:
>
> Jeff has been appointed to the role of integrating the SAS code
> with the Linux SCSI _model_, with James Bottomley's "transport
> attributes".
> So you can expect more patches from him.
So very soon now, with proof by code, we shall have confirmation or
negation of that assertion. I'll wait quietly for this to happen, and I
would suggest you do the same.
James
On Sep 30, 2005, at 15:08:15, Luben Tuikov wrote:
> On 09/30/05 14:50, Kyle Moffett wrote:
>> On Sep 30, 2005, at 14:34:42, Luben Tuikov wrote:
>>
>>> This is how we have the SPI-centric EH methods in the scsi host
>>> template right now:
>>> int (* eh_abort_handler)(struct scsi_cmnd *);
>>> int (* eh_device_reset_handler)(struct scsi_cmnd *);
>>> int (* eh_bus_reset_handler)(struct scsi_cmnd *);
>>> int (* eh_host_reset_handler)(struct scsi_cmnd *);
>>
>> So submit patches to fix it! You clearly understand what is
>> wrong, so why not help change it?
>
> Because
> - I do not want to give heart attack to all existing LLDDs
Significance of change is not an issue, assuming the change is broken
up into a collection of small obvious changes as highlighted in
Documentation/SubmittingPatches
> - Some LLDD would never be able to be changed
Why not? It's easy to change APIs, even stuff as invasive as the VM,
the device driver model, etc, and those get changed all the time.
> - Some LLDD work on very _scarce_ hardware which we cannot test.
You don't have to worry all that much about testing. If your patches
are small and obviously correct (like they should be), then they will
get enough review during submission that there will only be a very
small number of bugs. The few remaining bugs will probably be ironed
out in -mm. In any case, if nobody uses hardware anymore, eventually
the driver will get sufficiently crufty and out of date that it will
be recognized as such and removed.
> - plus such radical changes are neither warranted nor necessary.
Jeff Garzik et. al. seem to think that they are necessary, and I
agree. You don't need to fork SCSI-core; doing so would just double
the maintainer load, and _that_ is neither warranted nor necessary.
> It is better to keep legacy around, until all you'll have on your
> new serverboard is a SAS/SATA storage chip such as AIC-94xx or say
> BCM8603. Then you can compile out most of the legacy stuff.
Precisely. When nobody uses the legacy drivers to the point that
they aren't fixed or maintained anymore because no-one reports bugs,
then said drivers can be removed from the kernel entirely, along with
any support code. The model I describe here works better because it
keeps a _single_ clean core subsystem, and leaves any lack-of-
maintenance crap in the old drivers.
> I think not breaking anything (for now at least) would be the
> _easiest_ and most painless way to transition.
Until somebody wants to add a new high-level SCSI feature that works
for both the new and the old devices. Then they have to do it _twice_.
>>> The way we do this is we slowly, without disruption to older
>>> drivers introduce, in parallel, emerge a new, simpler, slimmer,
>>> faster SCSI Core, whereby we accommodate new infrastructures,
>>> yet, have 100% backward compatibility, via the current older SCSI
>>> Core. After all, both would be a bunch of functions in a bunch of
>>> files.
>>
>> Except this introduces bloat and multiplies maintainer load. Fix the
>> existing one. If it breaks other in-core drivers, fix those to
>
> Well, not necessarily. It would be more painful and more
> maintainer load if we did what you suggest. The overhead would be
> enormous.
So you're saying fixing the current SCSI subsystem once *now* costs
more than applying all *future* SCSI fixes to _two_ SCSI subsystems,
handling bug reports for _two_ SCSI subsystems, etc.
>> s/Politics.*//g; I hate politics. Keep it off this list.
>
> Me too, but we are idealists. Politics is an integral part of life.
Politics are not an integral part of productive technical
discussions, though. If you discuss technical topics and provide
realistic technical descriptions, examples, reasons, code, etc, then
politics tends not to matter in the discussion, and we're all happier
people.
Cheers,
Kyle Moffett
-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GCM/CS/IT/U d- s++: a18 C++++>$ UB/L/X/*++++(+)>$ P+++(++++)>$ L++++(+
++) E W++(+) N+++(++) o? K? w--- O? M++ V? PS+() PE+(-) Y+ PGP+++ t+(+
++) 5 X R? tv-(--) b++++(++) DI+ D+ G e->++++$ h!*()>++$ r !y?(-)
------END GEEK CODE BLOCK------
On 09/30/05 16:45, James Bottomley wrote:
> On Fri, 2005-09-30 at 14:34 -0400, Luben Tuikov wrote:
>
>>James, Linus, can we have this driver in the kernel now, please?
>
>
> A while ago I told you that if you could show that the transport class
> abstraction could not support both the aic94xx and LSI SAS cards then we
I have, by example and by spec. They both use two different
and distinct architectures.
Now _you_ have decided that this isn't the case, simply because
you want to prove your own idea. (which breaks SAM layering)
I think I explained the similarity of the SAS Transport Layer
to *USB and SBP*.
As I said: everyone wants a pice of the SAS code.
You do too.
I'm sure you'll do whatever humanly possible to show
that _your_ idea can be applied: you can do this now:
just use a big if () { ... } else { ... } statement and
you're done.
Furthermore I do not see the reasons to umbrella both
"aic94xx and LSI cards" when they are _completely different_
in architecture: MPT and open transport (ala USB Storage and SBP).
> could look at doing SAS differently. Since then you have asserted many
> times that a transport class could not work for the aic94xx (mostly by
> making inaccurate statements about what the transport class abstraction
> is) but have never actually provided any evidence for your assertion.
The code is here:
http://linux.adaptec.com/sas/
>>Now to things more pertinent, which I'm sure people are interested in:
>>
>>Jeff has been appointed to the role of integrating the SAS code
>>with the Linux SCSI _model_, with James Bottomley's "transport
>>attributes".
>>So you can expect more patches from him.
>
> So very soon now, with proof by code, we shall have confirmation or
> negation of that assertion. I'll wait quietly for this to happen, and I
> would suggest you do the same.
I just thought it was only fare to the rest of the community
to know how far the politics has escalated.
Everyone wants a piece of the SAS code.
Luben
> >>> The way we do this is we slowly, without disruption to older
> >>> drivers introduce, in parallel, emerge a new, simpler, slimmer,
> >>> faster SCSI Core, whereby we accommodate new infrastructures,
> >>> yet, have 100% backward compatibility, via the current older SCSI
> >>> Core. After all, both would be a bunch of functions in a bunch of
> >>> files.
> >>
> >> Except this introduces bloat and multiplies maintainer load. Fix the
> >> existing one. If it breaks other in-core drivers, fix those to
> >
> > Well, not necessarily. It would be more painful and more
> > maintainer load if we did what you suggest. The overhead would be
> > enormous.
>
> So you're saying fixing the current SCSI subsystem once *now* costs
> more than applying all *future* SCSI fixes to _two_ SCSI subsystems,
> handling bug reports for _two_ SCSI subsystems, etc.
>
Luben has more than once called for adding a small number of
additional calls to the existing SCSI core. These calls would
implement the new (reduced) functionallity. The old calls would
continue to support the full SPI functionallity. No existing LLDD
would need modification.
Then, over time, more radical restructuring could be done that pulls
SPI out of SCSI core.
I believe this proposal is what he was talking about, not the brand
new simplified SCSI core that has been discussed recently in this
thread.
Greg
--
Greg Freemyer
The Norcross Group
Forensics for the 21st Century
On 09/30/05 17:31, Kyle Moffett wrote:
> Jeff Garzik et. al. seem to think that they are necessary, and I
I've been contending this since before Jeff started work on
libata. But none of the ideas: 64 bit LUN, HCIL removal, etc.,
were accepted with "submit a patch".
> So you're saying fixing the current SCSI subsystem once *now* costs
> more than applying all *future* SCSI fixes to _two_ SCSI subsystems,
> handling bug reports for _two_ SCSI subsystems, etc.
I'm saying that the current "old" one is already obsolete,
when all you have is a SAS chip on your mainboard.
All you need is a small, tiny, fast, slim SCSI Core.
>>>s/Politics.*//g; I hate politics. Keep it off this list.
>>
>>Me too, but we are idealists. Politics is an integral part of life.
>
>
> Politics are not an integral part of productive technical
> discussions, though. If you discuss technical topics and provide
> realistic technical descriptions, examples, reasons, code, etc, then
> politics tends not to matter in the discussion, and we're all happier
> people.
Yes, please re-read this thread, and open and read all the
references I've included to SAM, SPC, SAS and SAT of T10.org.
Politics: "Nah, whatever you say, specs are *crap* and we'll
do it our way. We are not interested in your way, even if it
were better. Oh, and BTW, REQUEST SENSE clears ACA and LUN
is a u64."
See?
Luben
On Fri, 30 Sep 2005, Luben Tuikov wrote:
> Hi Andre,
>
> Let me know if this 4 section write up satisfies:
> Section 4: Politics
> -------------------
>
> Let's face it: SAS is a new emerging technology.
> It will be the technology for the next 10-15 years,
> and *everybody* in Linux SCSI wants a piece of it.
> Everybody wants their name and contribution to it.
No true, many of us could careless about credit list.
> This is fine, but we need people who clearly understand
> the technology and clearly understand what, how
> and why it works. We need well-read and well educated
> people. Linux dedication is fine, but protocol knowlege
> is needed too.
Sometimes teaching others is a better way to bring them around to your
view point while learning about their goals. Since everyone/most agree
your T10 knowledge is strong, others have pointed out you are savy enough
to work around problems over fixing them in general. Blah blah ...
Just show everyone why it can not work the "Linux Way" and defend the
points logically. Should the defense of it not be possible, then the
point is lost.
> Can Linux afford people who have never even read SAS
> to write SAS Code for Linux. Yes, sure. It is the
> Linux's ideology: "specs are cr@p".
SPECs become crap when organizations like STA with T10 make joining and
voting on the technology under NCITS $10,000.00 annual membership. This
is old boys club rules, otherwise I would have joined and terrorized T10
like I did to T13. Exclusion breeds distrust.
> Conclusion
> ----------
>
> Even though the SAS Transport Layer follows an _already_
> establised layering infrastructure for more (less?) exotic
> transports such as USB and SBP, James Bottomley has resisted
> its inclusion in Linux SCSI.
If this is accurate then it is fair to raise a question; however, few can
stand in judgement because they were present in for the discussions. The
remander (self included) are in the dark.
Cheers,
Andre
On 09/30/05 18:10, Greg Freemyer wrote:
>
> Luben has more than once called for adding a small number of
> additional calls to the existing SCSI core. These calls would
> implement the new (reduced) functionallity. The old calls would
> continue to support the full SPI functionallity. No existing LLDD
> would need modification.
>
> Then, over time, more radical restructuring could be done that pulls
> SPI out of SCSI core.
>
> I believe this proposal is what he was talking about, not the brand
> new simplified SCSI core that has been discussed recently in this
> thread.
See? There _are_ smart people out there.
Luben
On 09/30/05 18:04, Andre Hedrick wrote:
>
> No true, many of us could careless about credit list.
I wasn't talking about you. They know who they are.
> Sometimes teaching others is a better way to bring them around to your
> view point while learning about their goals. Since everyone/most agree
> your T10 knowledge is strong, others have pointed out you are savy enough
> to work around problems over fixing them in general. Blah blah ...
Thank you Andre.
> Just show everyone why it can not work the "Linux Way" and defend the
> points logically. Should the defense of it not be possible, then the
> point is lost.
I think I have. All the references to T10, all the pictures
to the email you replied to which you deleted, all the words.
> SPECs become crap when organizations like STA with T10 make joining and
> voting on the technology under NCITS $10,000.00 annual membership. This
> is old boys club rules, otherwise I would have joined and terrorized T10
> like I did to T13. Exclusion breeds distrust.
Well, the T10.org reflector is open to everyone.
Of course voting-membership is expensive. And it should be so.
They don't want every "Joe" (no offence to Joe or to LKML or LSML
participants) to participate.
If you are a voting member then you really have a reason, you really
know what you're talking about and voting for and you really are
serious. It means that you or your company care.
It also becoms quickly enough obvious if you know your stuff
after a meeting or two.
Luben
Greg Freemyer wrote:
> Luben has more than once called for adding a small number of
> additional calls to the existing SCSI core. These calls would
> implement the new (reduced) functionallity. The old calls would
> continue to support the full SPI functionallity. No existing LLDD
> would need modification.
IOW, what Luben wants is:
if (Luben)
do this
else
do current stuff
If this is the case, why bother touching drivers/scsi/* at all?
Regards,
Jeff
Luben Tuikov wrote:
> MPT-based drivers + James Bottomley's "transport attributes"
You continue to fail to see that a transport class is more than just
transport attributes.
You continue to fail to see that working on transport class support IS a
transport layer, that includes management.
Is you don't understand this fundamental stuff, how can we expect you to
get it right?
Jeff
Luben Tuikov wrote:
> But none of the ideas: 64 bit LUN, HCIL removal, etc.,
> were accepted with "submit a patch".
I concede this may have been the response in the past. Its not, now.
>>So you're saying fixing the current SCSI subsystem once *now* costs
>>more than applying all *future* SCSI fixes to _two_ SCSI subsystems,
>>handling bug reports for _two_ SCSI subsystems, etc.
>
>
> I'm saying that the current "old" one is already obsolete,
> when all you have is a SAS chip on your mainboard.
>
> All you need is a small, tiny, fast, slim SCSI Core.
Then don't use it at all. Write a block driver, if you really feel we
need two SCSI cores.
> Politics: "Nah, whatever you say, specs are *crap* and we'll
> do it our way. We are not interested in your way, even if it
> were better. Oh, and BTW, REQUEST SENSE clears ACA and LUN
> is a u64."
This is a misrepresentation. -We- understand the stuff you have posted.
But you continue to demonstrate that you simply do not understand the
existing SCSI core code.
The SAS transport class supports commonality across all SAS
implementations. This includes both MPT and Adaptec 94xx.
SAS transport class + libsas supports software implementations of SAS,
including transport layer management. This includes Adaptec 94xx but
NOT MPT.
Jeff
Luben Tuikov wrote:
> I'm sure you'll do whatever humanly possible to show
> that _your_ idea can be applied: you can do this now:
> just use a big if () { ... } else { ... } statement and
> you're done.
This is not how we do things in Linux. You're doubling the maintenance
burden.
If you really want to do this, at least don't fill up drivers/scsi/ with
an additional, completely unrelated codepath.
> Furthermore I do not see the reasons to umbrella both
> "aic94xx and LSI cards" when they are _completely different_
> in architecture: MPT and open transport (ala USB Storage and SBP).
There is commonality between aic94xx and MPT/LSI stuff. aic94xx SAS
transport layer is a superset of MPT/LSI SAS transport: it clearly
needs far more management code.
We understand this. The part you don't understand is that we want to
emphasize the commonality, rather than let aic94xx and MPT/LSI go in
completely different directions.
Read it again: aic94xx/BCMxxx is a superset of functionality, not
completely different.
Jeff
On Fri, Sep 30, 2005 at 07:54:08PM -0400, Jeff Garzik wrote:
> Greg Freemyer wrote:
> >Luben has more than once called for adding a small number of
> >additional calls to the existing SCSI core. These calls would
> >implement the new (reduced) functionallity. The old calls would
> >continue to support the full SPI functionallity. No existing LLDD
> >would need modification.
>
> IOW, what Luben wants is:
>
> if (Luben)
> do this
> else
> do current stuff
>
> If this is the case, why bother touching drivers/scsi/* at all?
that's the reason why I proposed that this moved to drivers/sas/* or
somewhere else so that there is no maintaining conflict.
Regards,
Willy
On 09/30/05 19:54, Jeff Garzik wrote:
> Greg Freemyer wrote:
>
>>Luben has more than once called for adding a small number of
>>additional calls to the existing SCSI core. These calls would
>>implement the new (reduced) functionallity. The old calls would
>>continue to support the full SPI functionallity. No existing LLDD
>>would need modification.
>
>
> IOW, what Luben wants is:
>
> if (Luben)
> do this
> else
> do current stuff
>
> If this is the case, why bother touching drivers/scsi/* at all?
In order to have a new better, faster, slimmer SCSI Core.
Luben
On 09/30/05 19:57, Jeff Garzik wrote:
> Luben Tuikov wrote:
>
>>MPT-based drivers + James Bottomley's "transport attributes"
>
>
> You continue to fail to see that a transport class is more than just
> transport attributes.
>
> You continue to fail to see that working on transport class support IS a
> transport layer, that includes management.
>
> Is you don't understand this fundamental stuff, how can we expect you to
> get it right?
>From what I see, because of its *layering* position
JB's "transport attributes" cannot satisfy open transport.
The reason is that MPT-based drivers indeed do need host template
in the LLDD.
Open Transport (SBP/USB/SAS) do not, since the chip is only
an interface to the transport.
The host template is implemented by a transport layer,
say USB Storage or the SAS Transport Layer.
This allows you to do great things, like layer
intersection.
Luben
On 09/30/05 20:33, Jeff Garzik wrote:
> Luben Tuikov wrote:
>
>>But none of the ideas: 64 bit LUN, HCIL removal, etc.,
>>were accepted with "submit a patch".
>
>
> I concede this may have been the response in the past. Its not, now.
>
>
>
>
>>>So you're saying fixing the current SCSI subsystem once *now* costs
>>>more than applying all *future* SCSI fixes to _two_ SCSI subsystems,
>>>handling bug reports for _two_ SCSI subsystems, etc.
>>
>>
>>I'm saying that the current "old" one is already obsolete,
>>when all you have is a SAS chip on your mainboard.
>>
>>All you need is a small, tiny, fast, slim SCSI Core.
>
>
> Then don't use it at all. Write a block driver, if you really feel we
> need two SCSI cores.
>
>
>
>>Politics: "Nah, whatever you say, specs are *crap* and we'll
>>do it our way. We are not interested in your way, even if it
>>were better. Oh, and BTW, REQUEST SENSE clears ACA and LUN
>>is a u64."
>
>
> This is a misrepresentation. -We- understand the stuff you have posted.
>
> But you continue to demonstrate that you simply do not understand the
> existing SCSI core code.
>
> The SAS transport class supports commonality across all SAS
> implementations. This includes both MPT and Adaptec 94xx.
>
> SAS transport class + libsas supports software implementations of SAS,
> including transport layer management. This includes Adaptec 94xx but
> NOT MPT.
You almost get it right, other than the layering infrastructure.
The SAS Transport Layer is a layer in its own right. It is not
a "libsas".
MPT and open transport a very different, one hides the transport,
i.e. the transport layer is in firmware; the other exposes it
and needs a transport layer. See the pictures here:
http://marc.theaimsgroup.com/?l=linux-kernel&m=112810649712793&w=2
Luben
On 10/01/05 00:58, Willy Tarreau wrote:
> On Fri, Sep 30, 2005 at 07:54:08PM -0400, Jeff Garzik wrote:
>
>>Greg Freemyer wrote:
>>
>>>Luben has more than once called for adding a small number of
>>>additional calls to the existing SCSI core. These calls would
>>>implement the new (reduced) functionallity. The old calls would
>>>continue to support the full SPI functionallity. No existing LLDD
>>>would need modification.
>>
>>IOW, what Luben wants is:
>>
>> if (Luben)
>> do this
>> else
>> do current stuff
>>
>>If this is the case, why bother touching drivers/scsi/* at all?
>
>
> that's the reason why I proposed that this moved to drivers/sas/* or
> somewhere else so that there is no maintaining conflict.
Yes, it has been moved already there.
http://linux.adaptec.com/sas/
Luben
On 09/30/05 20:38, Jeff Garzik wrote:
> Luben Tuikov wrote:
>
>>I'm sure you'll do whatever humanly possible to show
>>that _your_ idea can be applied: you can do this now:
>>just use a big if () { ... } else { ... } statement and
>>you're done.
>
>
> This is not how we do things in Linux. You're doubling the maintenance
> burden.
No necessarily. See below.
> If you really want to do this, at least don't fill up drivers/scsi/ with
> an additional, completely unrelated codepath.
How do you say it is unrelated?
Is USB storage unrelated? (other than the fact that it doesn't live
in drivers/scsi/)
> There is commonality between aic94xx and MPT/LSI stuff. aic94xx SAS
> transport layer is a superset of MPT/LSI SAS transport: it clearly
> needs far more management code.
And MPT/LSI SAS does not need this managament as this layer
is completely implemented in FW and not exposed (and for a reason).
> We understand this. The part you don't understand is that we want to
> emphasize the commonality, rather than let aic94xx and MPT/LSI go in
> completely different directions.
But this was LSI's decision, remember? We did work together,
until LSI and Dell decided that they'd rather let Christoph do it.
(Since who cares about the technological merit of the code when it
will be accepted into the kernel?)
Now you want to integrate the two? Apparently LSI and Dell haven't
made up their mind.
As I said: Vendors are completely playing to the tune of a couple
of people at linux-scsi, for this reason we haven't seen _any_
SCSI or Storage _innovation_ in SCSI Core.
As opposed to those vendors saying: We _really_ need 64 bit LUNS
and it would be really nice to get rid of HCIL, etc, etc.
If all vendors pushed for that and were not afraid to speak
up (because they have drivers to write and patches to submit
and want acceptance), then SCSI Core would be a better place.
IMO, 64 bit LUNs and no HCIL is more important than "transport
attributes" and should've _preceded_ them.
The fact that you're trying to umbrella them together, doesn't
make it _technologically_ correct.
Remember, a person's fall starts when they're surrounded by "Yes" men.
> Read it again: aic94xx/BCMxxx is a superset of functionality, not
> completely different.
One implements all transport related tasks in FW and exposes only LUs
to the LLDD, the other implements only the interface to the transport
in the chip (the interconnect), and the rest is handed to upper layers.
If you sit down with a clean sheet of _paper and a pencil_ and try
to draw out the layering infrastructure for both and how they
interface with SCSI Core, you'll see that with MPT, things are
_upside_ down compared to USB/SBP/SAS. Now trying to reconcile both,
while possible, would be extremely _ugly_, unless say, you can fake out
event formation in an MPT based LLDD, but then again, you'd need to
resolve the host template thing...
It would just be extremely ugly and not as flowing and straightforward
as the current code is.
Luben
Luben Tuikov wrote:
> On 09/30/05 19:57, Jeff Garzik wrote:
>>Luben Tuikov wrote:
>>>MPT-based drivers + James Bottomley's "transport attributes"
>>You continue to fail to see that a transport class is more than just
>>transport attributes.
>>
>>You continue to fail to see that working on transport class support IS a
>>transport layer, that includes management.
>>
>>Is you don't understand this fundamental stuff, how can we expect you to
>>get it right?
>
>
>>From what I see, because of its *layering* position
> JB's "transport attributes" cannot satisfy open transport.
Repeating verbatim the above quote: a transport class is more than just
transport attributes.
> The reason is that MPT-based drivers indeed do need host template
> in the LLDD.
> Open Transport (SBP/USB/SAS) do not, since the chip is only
> an interface to the transport.
> The host template is implemented by a transport layer,
> say USB Storage or the SAS Transport Layer.
Every chip is ultimately an interface to the transport, regardless of
whether the transport layer is largely managed by software (aic94xx) or
firmware (MPT). SCSI host template can work just fine with open
transport hardware.
Jeff
Luben Tuikov wrote:
> On 09/30/05 20:33, Jeff Garzik wrote:
>>This is a misrepresentation. -We- understand the stuff you have posted.
>>
>>But you continue to demonstrate that you simply do not understand the
>>existing SCSI core code.
>>
>>The SAS transport class supports commonality across all SAS
>>implementations. This includes both MPT and Adaptec 94xx.
>>
>>SAS transport class + libsas supports software implementations of SAS,
>>including transport layer management. This includes Adaptec 94xx but
>>NOT MPT.
>
>
> You almost get it right, other than the layering infrastructure.
>
> The SAS Transport Layer is a layer in its own right. It is not
> a "libsas".
Different open transport hardware will expose the underlying network at
different levels.
Hardware A might provide direct access to SSP and IDENTIFY/CONNECT frame
handling, while Hardware B may handle that internally, while still
providing full SMP access for the transport layer to discovery topology
and build its routing table.
We cannot assume that all open transport hardware will function the
same, hence the better approach is a library of helpers that function in
concert with LLDD to form a transport layer.
> MPT and open transport a very different, one hides the transport,
> i.e. the transport layer is in firmware; the other exposes it
For the 1001th time, we know all this.
Jeff
On 10/03/05 11:57, Jeff Garzik wrote:
>>From what I see, because of its *layering* position
>>JB's "transport attributes" cannot satisfy open transport.
>
>
> Repeating verbatim the above quote: a transport class is more than just
> transport attributes.
a) "Transport Attributes" _is_ its name,
b) It sits across SCSI Core, i.e. on the same level.
c) It was never intended to add management.
d) Its inteface to SCSI Core is badly defined and an "invention",
(and very poor at that).
The reason for d) is that
1) it tries to unify different _transports_,
2) does _not_ follow _any_ spec or standard.
Look at this, while you repeat verbaitm a single
quote, I give you technical arguments, then you just
repeat a single quote verbatim... Sad.
> Every chip is ultimately an interface to the transport, regardless of
> whether the transport layer is largely managed by software (aic94xx) or
> firmware (MPT). SCSI host template can work just fine with open
> transport hardware.
Maybe the picures and the write up here will help:
http://marc.theaimsgroup.com/?l=linux-kernel&m=112810649712793&w=2
Luben
Luben Tuikov wrote:
> As opposed to those vendors saying: We _really_ need 64 bit LUNS
> and it would be really nice to get rid of HCIL, etc, etc.
Everybody agrees with this 100%
Note that James submitted a sdev_printk() patch in the past few days,
which assists in removing HCIL from the SCSI core.
> IMO, 64 bit LUNs and no HCIL is more important than "transport
> attributes" and should've _preceded_ them.
Agreed. But that's a lot of work, and I doubt people want to delay SAS
further to wait for complete HCIL elimination.
> The fact that you're trying to umbrella them together, doesn't
> make it _technologically_ correct.
It's muddled together, yes. That doesn't make it any less correct.
It's just not a clean, immediate separation. Its a separation that
takes time.
Jeff
Luben Tuikov wrote:
> On 10/03/05 11:57, Jeff Garzik wrote:
>
>>>From what I see, because of its *layering* position
>>
>>>JB's "transport attributes" cannot satisfy open transport.
>>
>>
>>Repeating verbatim the above quote: a transport class is more than just
>>transport attributes.
>
>
> a) "Transport Attributes" _is_ its name,
No, transport class is its name. Think about a standard object-oriented
paradigm. Each transport has unique characteristics. The proper place
to export these and manage these characteristics is the transport layer,
as SAM agrees. The manifestation of the transport layer is the
transport class.
You have to look beyond the current code, to see this.
An implementation of a transport class, in conjunction with helper
functions common to all transports (SCSI core), combines to form the
transport layer for a specific transport.
> b) It sits across SCSI Core, i.e. on the same level.
> c) It was never intended to add management.
SCSI core is nothing but a set of helper functions and support code that
enable the transport class and LLDD to implement the transport layer.
> d) Its inteface to SCSI Core is badly defined and an "invention",
> (and very poor at that).
Strongly disagree. This invention is defined by -needs-, as is other
code in Linux. If we have new needs, we change the code.
> The reason for d) is that
> 2) does _not_ follow _any_ spec or standard.
That's fine, since its an internal kernel API.
Jeff
On 10/03/05 12:48, Jeff Garzik wrote:
> No, transport class is its name. Think about a standard object-oriented
Not according to Kconfig:
menu "SCSI Transport Attributes"
depends on SCSI
config SCSI_SPI_ATTRS
tristate "Parallel SCSI (SPI) Transport Attributes"
depends on SCSI
help
If you wish to export transport-specific information about
each attached SCSI device to sysfs, say Y. Otherwise, say N.
config SCSI_FC_ATTRS
tristate "FiberChannel Transport Attributes"
depends on SCSI
help
If you wish to export transport-specific information about
each attached FiberChannel device to sysfs, say Y.
Otherwise, say N.
config SCSI_ISCSI_ATTRS
tristate "iSCSI Transport Attributes"
depends on SCSI
help
If you wish to export transport-specific information about
each attached iSCSI device to sysfs, say Y.
Otherwise, say N.
config SCSI_SAS_ATTRS
tristate "SAS Transport Attributes"
depends on SCSI
help
If you wish to export transport-specific information about
each attached SAS device to sysfs, say Y.
endmenu
> paradigm. Each transport has unique characteristics. The proper place
> to export these and manage these characteristics is the transport layer,
> as SAM agrees.
But:
> The manifestation of the transport layer is the
> transport class.
Bzzzt! Wrong.
This is where you and James Bottomley make the wrong assesment.
Having the SCSI host template in the LLDD tells everyone immeditealy
that you have it all wrong as far as anything SAM/SPC is concerned.
Look at any transport spec, how little SCSI Host template is there.
You need to understand that declaring the host template in the
LLDD is, and has always been, the _exception_, not the rule.
The reason is legacy Parallel SCSI.
It is MPT based drivers who are the exception, not the rule,
and JB's "transport attributes" makes it the rule, and a
transport layer (what you call libsas), the exception.
It is wrong for a host template to "branch out" to a
transport layer as you're doing it now. Think about it.
The layering infrastructure is upside down.
> You have to look beyond the current code, to see this.
Eh, well, not that you put it like this, I expect that
you'll completely pull out the implementation from my code
and put it in the "transport attributes" and call it your own.
I don't want to look beyond the current code, I'm discussing
things now, as they are. How many times is JB going to change
the "transport attributes" just because FC needed one more thing
or because of, as often has been recently seen, "brown paper bag"
fix?
> An implementation of a transport class, in conjunction with helper
> functions common to all transports (SCSI core), combines to form the
> transport layer for a specific transport.
Should:
The transport layer sits below SCSI Core and above the LLDD.
SCSI Core is completely unaware of the transport layer.
The LLDD communicates with the transport layer via
the event interface (as shown in the SAS Transport layer)
and the transport layer communicates with the LLDD via
the Execute Command SCSI RPC and TMF. All as outlined here:
http://marc.theaimsgroup.com/?l=linux-scsi&m=112629423714248&w=2
>>b) It sits across SCSI Core, i.e. on the same level.
>>c) It was never intended to add management.
>
>
> SCSI core is nothing but a set of helper functions and support code that
> enable the transport class and LLDD to implement the transport layer.
Again you fail to see that the LLDD should _not_ implement
the host template as has been traditionally done.
The reason with this is that simply the LLDD has nothing to do
with the host template. Unless you're dealing with MPT-based
LLDD which implement everything in FW and export LUs to
SCSI Core (which is fine too, as long as they do not dictate
how SCSI Core should work).
Notice that for MPT-based solution, SCSI Core wouldn't even
do LU discovery (unless you can turn that off via FW dependent
ways).
>>d) Its inteface to SCSI Core is badly defined and an "invention",
>> (and very poor at that).
>
> Strongly disagree. This invention is defined by -needs-, as is other
> code in Linux. If we have new needs, we change the code.
You defence of your friends architecture is duly noted.
But if, as has been pointed out, you take a look at the
evolvement of this "invention" you'll see how it was and still
is _meandering_ in the technological maze to find its place.
All the while a transport layer like USB/SPB/SAS and maybe
iSCSI just sits "right". Think about it.
>>The reason for d) is that
>>2) does _not_ follow _any_ spec or standard.
>
>
> That's fine, since its an internal kernel API.
Now, lets shove it down the throat of eveybody.
You forgot to say something about
1) it tries to unify different _transports_.
I don't expect a blurb on that, btw.
Luben
Luben Tuikov wrote:
> On 09/30/05 19:57, Jeff Garzik wrote:
>
>>Luben Tuikov wrote:
>>
>>
>>>MPT-based drivers + James Bottomley's "transport attributes"
>>
>>
>>You continue to fail to see that a transport class is more than just
>>transport attributes.
>>
>>You continue to fail to see that working on transport class support IS a
>>transport layer, that includes management.
>>
>>Is you don't understand this fundamental stuff, how can we expect you to
>>get it right?
>
>
>>From what I see, because of its *layering* position
> JB's "transport attributes" cannot satisfy open transport.
>
> The reason is that MPT-based drivers indeed do need host template
> in the LLDD.
>
> Open Transport (SBP/USB/SAS) do not, since the chip is only
> an interface to the transport.
>
> The host template is implemented by a transport layer,
> say USB Storage or the SAS Transport Layer.
>
I think I can understand some of Luben's reasons for the layering. We
are facing similar problems with software iscsi and hw iscsi. For
software iscsi it would be nice to consolodate some of the common
software iscsi code into a layer or lib. Following Luben's path for
example our queuecommand would be:
scsi-ml -> scsi_host_template->queuecommand -> iscsi transport common
queuecommand (do things like check session state, that we are not in
session level recovery, scsi to iscsi pdu prep like setting the data
direction, and other iSCSI PDU prep) -> iscsi_transport module ->
iscsi_transport->queuepdu (you can probably reccomend a better name) ->
tcp, sctp, iwarp, or some iSCSI HW that exposes a iSCSI interface rather
than SCSI (note that qla4xxx would use its own
scsi_host_template->queuecommand since it does not expose enough iSCSI
internals for it to be useful to plug in here).
However, HW iscsi cards and software/partial-software iscsi solutions
can share code for things like session and connection creation where we
would have transport class lib functions:
iscsi_add_session/iscsi_remove_session which both the HW iscsi cards
like qla4xxx and software/partial-software iscsi drivers could use to
setup things like a common sysfs representation.
iscsi_add_session/iscsi_remove_session would work similar to the
fc_rport code where the midlayer doesn't really know they exist (this is
similar to our session and connection code today but it is bound to the
scsi host which prevents qla4xxx from using it).
Is the direction we are going where iscsi would have to put the "iscsi
transport common queuecommand" code into something similar to libata? Or
is it that Luben's transport layer code is performing something
different than software/partial-software iscsi?
Luben Tuikov wrote:
> On 10/03/05 12:48, Jeff Garzik wrote:
>
>>No, transport class is its name. Think about a standard object-oriented
>
>
> Not according to Kconfig:
>
> menu "SCSI Transport Attributes"
> depends on SCSI
>
> config SCSI_SPI_ATTRS
> tristate "Parallel SCSI (SPI) Transport Attributes"
> depends on SCSI
> help
> If you wish to export transport-specific information about
> each attached SCSI device to sysfs, say Y. Otherwise, say N.
>
> config SCSI_FC_ATTRS
> tristate "FiberChannel Transport Attributes"
> depends on SCSI
> help
> If you wish to export transport-specific information about
> each attached FiberChannel device to sysfs, say Y.
> Otherwise, say N.
>
For FC there is code like the fc_rport stuff which exports a sysfs
interface but also does a lot more like probing and queue blocking.
> config SCSI_ISCSI_ATTRS
> tristate "iSCSI Transport Attributes"
> depends on SCSI
> help
> If you wish to export transport-specific information about
> each attached iSCSI device to sysfs, say Y.
> Otherwise, say N.
And the iSCSI class does do a lot more now too. This just has not been
updated. It handles the userspace to kernel communication, session and
connection sysfs interface setup, and there were some patches that added
the ability to tell scsi-ml to stop queueing commands to a iscsi driver.
Structures like the fc_rport and iscsi_session are managed by the
transport classes so scsi-ml never knows about them (except for that
scanning bug). And it is possible to share them between HW and software
or partial software solutions. I do agree for some iscsi sitautions
having a layer over the eh or command exection where the transport
really is more of a layer like your design would be nice (I am not
refferring to the code duplication though becuase iSCSI would like some
of yrou fixes :), but at the same time there are places where code can
be shared between a interface that hides the lower level details and one
that implements them in software. Maybe it is not this way for SAS though.
Mike Christie wrote:
> For FC there is code like the fc_rport stuff which exports a sysfs
> interface but also does a lot more like probing and queue blocking.
> And the iSCSI class does do a lot more now too. This just has not been
> updated. It handles the userspace to kernel communication, session and
> connection sysfs interface setup,
Great. Exactly.
> Structures like the fc_rport and iscsi_session are managed by the
> transport classes so scsi-ml never knows about them (except for that
> scanning bug). And it is possible to share them between HW and software
> or partial software solutions. I do agree for some iscsi sitautions
> having a layer over the eh or command exection where the transport
> really is more of a layer like your design would be nice (I am not
> refferring to the code duplication though becuase iSCSI would like some
> of yrou fixes :), but at the same time there are places where code can
> be shared between a interface that hides the lower level details and one
> that implements them in software. Maybe it is not this way for SAS though.
Adaptec's SAS stuff implements the standard high level SCSI model as an
API, which is a pretty decent direction for SCSI long term: provides a
transport-independent execute-scsi-command high level hook (along with
the other task management functions), and hides the transport details
for the most part.
That's fine, and works for iSCSI as well.
I just disagree that we need to have two concurrent APIs for SCSI,
completely separate from each other, and mildly duplicating each other's
code.
The current SCSI code will morph in the proper direction given time and
love. Segregating generic [SPI | FC | SAS | iSCSI | ATA | RAID | ...]
transport layer code into their own modules -- the transport classes and
associated libs -- will point out the sore spots where scsi-ml needs
changes. This approach also implies we improve the existing scsi-ml
where needed, rather than the proposed "if legacy, let it bitrot" approach.
Jeff
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