RE: How to add/drop SCSI drives from within the driver?

[Mukker, Atul]

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:James.Bottomley@xxxxxxxxxxxx] 
> Sent: Wednesday, December 15, 2004 1:49 PM
> To: Matt Domsch
> Cc: Salyzyn, Mark; Bagalkote, Sreenivas; brking@xxxxxxxxxx; 
> Linux Kernel; SCSI Mailing List; bunk@xxxxxxxxx; 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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