Date: Sat, 18 Sep 2004 14:30:23 -0700
From: Greg KH <greg@kroah.com>
To: "Ihar 'Philips' Filipau" <filia@softhome.net>
Cc: Linux Kernel ML <linux-kernel@vger.kernel.org>
Subject: Re: udev is too slow creating devices
Message-ID: <20040918213023.GB1901@kroah.com>
References: <414C9003.9070707@softhome.net>
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On Sat, Sep 18, 2004 at 09:44:03PM +0200, Ihar 'Philips' Filipau wrote:
> >That will be soon going away with my multi-threaded device discovery
> >work.  And I run pci hotplug boxes (and so do all of the PCMCIA/CardBus
> >users), so don't discard PCI from being a async bus type :)
> >
> >Async is now the norm, and drivers like the microcode module are the
> >exception.
> 
>   I wanted you to say that.
> 
>   That's wrong attitude. I'm working on workstation where 95% of 
> hardware plugged 100% of time. That's not exception. Not eerything is 
> hot-pluggable USB/FireWire/whatever.

Do you have PCI devices?  pnp-isa devices?  Ok, those all are
"hotpluggable" as far as the kernel is concerned.  They are loaded on
demand by userspace when the kernel sees the device.

If not, what kind of devices do you have?  The only place the
"on-demand" loading of modules doesn't work is for embedded systems that
have no way of discovering their devices, and need to be hardcoded in
the kernel.  But people are working on that :)

>   Event-based hot-plug scripts are great thing. As an implementation. 
> But user cares about one thing: 'modprobe usb-storage; mount /whatever' 
> working reliably.

No, they want to plug in their device and have the proper module
automatically loaded, and then the device mounted and the icon show up
on their desktop all automatically.  With hotplug and its helpers (udev,
/etc/dev.d/ and HAL) this all works just fine today.

>   /etc/dev.d probably great thing - but I'm not going to implement FSM 
> into every shell script which does modprobe for sake being Ok with 
> dynamic /dev/.

Fine, I'm not forcing you to do anything you don't want to do.  It
sounds like you like polling for your device nodes.  Great, live with
that, it is one way to do this :)

>   You need to change your attitude for first.

Change it to what?  A combative one?  Gladly :)

> For second - come up with a way for user space to block until device
> is here, and if it is not here/error detected - fail.

Please explain (with code) how to do that for something as "simple" as
the usb-storage driver.  Then we can continue this discussion.

>   As it was said before - /all/ we need, is to be able to tell 
> discovery phase from idle state of driver. "/All/" is quite much here - 
> but it must be a goal.

Wrong.  Our goal is to make Linux "just work".  And that is what is
happening today.  This "wait for modprobe" stuff helps no one.

>   I'm absolutely sure, that for PCI devices it is implementable quite 
> easy - probing is already done outside of modules. And we know precisely 
> are we Ok, or are we not. And we know when we are done. If it is not so 
> for USB yet - then it is bug which must be fixed.

PCI and USB both use the same probe core code.  So it works the same :)

You think you are grumpy now, just wait till I add threads to the probe
code...

thanks,

greg k-h
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