All right! The implementation is complete for this and the driver has
thoroughly gone through testing. Everything looks good except for a minor
glitch.
After the new logical drives are created with "- - -" written to the
scsi_host scan attribute, there is a highly noticeable delay before device
names (e.g., sda) appears in the /dev directory. If the management
application tried to access the device immediately after creating new, the
access fails. Putting a 1 second delay helped, but of course this is not a
deterministic solution.
What are the other possibilities?
Thanks
-Atul Mukker
LSI Logic
> -----Original Message-----
> From: James Bottomley [mailto:[email protected]]
> Sent: Wednesday, December 15, 2004 1:49 PM
> To: Matt Domsch
> Cc: Salyzyn, Mark; Bagalkote, Sreenivas; [email protected];
> Linux Kernel; SCSI Mailing List; [email protected]; Andrew
> Morton; Ju, Seokmann; Doelfel, Hardy; Mukker, Atul
> Subject: Re: How to add/drop SCSI drives from within the driver?
>
> On Wed, 2004-12-15 at 01:24 -0600, Matt Domsch wrote:
> > James, I've been thinking about this a little more, and you
> may be on
> > to something here. Let each driver add files as such:
> >
> > /sys/class/scsi_host
> > |-- host0
> > | |-- add_logical_drive
> > | |-- remove_logical_drive
> > | `-- rescan_logical_drive
> >
> > Then we can go 2 ways with this.
> > 1) driver functions directly call scsi_add_device(),
> > scsi_remove_device(), and something for rescan (option 2
> handles this
> > one cleanly for us). ATM, megaraid_mbox doesn't implement a rescan
> > function, so this point may be moot.
> >
> > 2) driver functions call a midlayer library function, which invokes
> > /sbin/hotplug with appropriate data, and add a new /etc/hotplug.d
> > helper app which would then write to these files:
> >
> > /sys/class/scsi_host
> > |-- host0
> > | |-- scan
> > /sys/devices/pci0000:0x/0000:0x:0x.0/host0
> > |-- 0:0:0:0
> > | |-- delete
> > | |-- rescan
> >
> > to do likewise.
>
> I'll buy this (option 2).. it seems like a good way to export
> the megaraid specific information and at the same time
> integrate it more fully into the evolving hotplug infrastructure.
>
> James
>
>
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On Fri, 2005-01-21 at 17:11 -0500, Mukker, Atul wrote:
> All right! The implementation is complete for this and the driver has
> thoroughly gone through testing. Everything looks good except for a minor
> glitch.
That's good news.
> After the new logical drives are created with "- - -" written to the
> scsi_host scan attribute, there is a highly noticeable delay before device
> names (e.g., sda) appears in the /dev directory. If the management
> application tried to access the device immediately after creating new, the
> access fails. Putting a 1 second delay helped, but of course this is not a
> deterministic solution.
>
> What are the other possibilities?
Well, how about hotplug. The device addition actually triggers a hot
plug event already (there's no need to add anything, it's done by the
mid-layer), so if you just listen for that, you'll know when the scan
has detected a device.
James