Re: [PATCH] 2.4.19 scsi_rescan patch (2nd pass)

[Patrick Mansfield <patmans@us.ibm.com>]

On Wed, Oct 02, 2002 at 12:56:06PM -0400, Doug Ledford wrote:
> On Wed, Oct 02, 2002 at 09:40:06AM -0700, Cress, Andrew R wrote:

> >   3) Other external disk enclosure (JBOD) that doesn't expose a 
> >      SAF-TE or SES interface.
> >      This case is out in the cold without the kernel-level rescan.
> > 
> > I'm disregarding case (1), since my target customer environment won't
> > tolerate the manual step.
> 
> You can forget 3 as well.  It's simply not reasonable to tie up a busy bus 
> with very long selection timeouts to "poll scan" a bus for new insertions.  
> Not gonna happen.  If the JBOD doesn't expose a reasonable interface, then 
> hot plug with it isn't supported in linux.  If it exposes something other 
> than SAF-TE or SES then the protocol it does support needs to be added to 
> the daemon in #2 in order for it to be supported.

For SCSI parallel yes, but for FCP (at least on a switch, I'm not sure about
loop), scanning won't have such a negative affect. With 2.5.x targets can
invoke a device_register and so a hotplug event (FCP adapter driver
changes required), and then the new target could be scanned (somehow via
user space trigger calling scan_scsis for a single host/channel/target id)
without affecting other targets on the switch.

-- Patrick Mansfield

> 
> 
> -- 
>   Doug Ledford <dledford@redhat.com>     919-754-3700 x44233