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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] Re: [PATCH] scsi: Make device scsi-disk reject
	/dev/sg*
Date: Sun, 28 Feb 2010 01:45:37 +0000
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To: qemu-devel@nongnu.org
Cc: Gerd Hoffmann <kraxel@redhat.com>, Markus Armbruster <armbru@redhat.com>

> On 02/25/10 11:23, Markus Armbruster wrote:
> > You're supposed to use scsi-generic for that.  Which rejects anything
> > but /dev/sg*.
> 
> Well, it isn't *that* easy.  The SG_IO ioctl used by scsi-generic works
> on tons of devices in linux, not only /dev/sg*.  I've seen patches
> floading around which change the check bdrv_is_sg() into "try SG_IO and
> see if it works", which would allow to use /dev/sda with both scsi-disk
> and scsi-generic depending on what you want.  Which makes alot of sense.
> 
> Making that change needs some extra care though to avoid existing
> configurations switching from scsi-disk to scsi-generic unnoticed.

Don't we really want to be testing !bdrv_is_block() ?

Paul