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Date: Mon, 17 Jun 2002 13:33:27 +0200
From: Kurt Garloff <garloff@suse.de>
To: John Summerfield <summer@os2.ami.com.au>
Cc: Linux kernel list <linux-kernel@vger.kernel.org>,
       Linux SCSI list <linux-scsi@vger.kernel.org>
Subject: Re: /proc/scsi/map
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Hi John,

On Sat, Jun 15, 2002 at 10:08:54PM +0800, John Summerfield wrote:
> > Life would be easier if the scsi subsystem would just report which SCSI
> > device (uniquely identified by the controller,bus,target,unit tuple) be=
longs
> > to which high-level device. The information is available in the kernel.
>=20
> Does this not fail if I pull a device off, change its ID (perhaps to fit
> into another system), then plug it in again? Or if I move it from one
> adaptor to another? =20

Sure it does.
The kernel can offer you the knowledge of a hardware path to your device,
which is given by controller,bust,SCSI target and unit numbers. This is
pretty stable in most configurations.

If you want to have more, you will probably use some sort of signatures.

But that's nothing which happens at SCSI layer.
For plain old SCSI devices, you may e.g. inquire the serial number (INQUIRY,
page code 0x80) which gives you a unique identifier if combined with
vendor and model strings. scsidev does this for you. But it occasinally
fails, as the open on scsi device may fail and we don't know the relation
between the sg devices (that can be used reliably to collect such
information) and the other high level devices. /proc/scsi/map solves this.

Regards,
--=20
Kurt Garloff  <garloff@suse.de>                          Eindhoven, NL
GPG key: See mail header, key servers         Linux kernel development
SuSE Linux AG, Nuernberg, DE                            SCSI, Security

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