[garloff@suse.de: Re: [linux-usb-devel] Re: /proc/scsi/map]

[garloff@suse.de: Re: [linux-usb-devel] Re: /proc/scsi/map]

[Kurt Garloff]

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Hi,

forgot to Cc: the other recipients. 
I did not want to turn this into a private discussion.

----- Forwarded message from Kurt Garloff <garloff@suse.de> -----

Date: Mon, 17 Jun 2002 02:46:24 +0200
From: Kurt Garloff <garloff@suse.de>
To: James Bottomley <James.Bottomley@steeleye.com>
Subject: Re: [linux-usb-devel] Re: /proc/scsi/map
In-Reply-To: <200206162314.g5GNEYf03058@localhost.localdomain>
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Hi,

On Sun, Jun 16, 2002 at 06:14:33PM -0500, James Bottomley wrote:
> oliver@neukum.name said:
> > But the drivers already know, or would have to be taught to know about
> > it. Somewhence that information has to come. You cannot avoid that
> > effort. 
> 
> Not necessarily: consider the SCSI WWN, which is supported by most modern SCSI 
> devices.  The driver never probes for or asks for this.  Nowhere in the 
> current SCSI code do we ask for this.  However user level commands (like 
> sg_inq) can formulate the 0x83 page inquiry to get this and return the output. 
>  This works today with the current driver.

This may work for your disks. You just can't open the device node for a
tape, if there is no medium inserted. If you know the mapping between
to a sg device you can use it.
That's the second piece of information that /proc/scsi/map provides.

The first piece is that the kernel tells kernel tells you the way it is
attached by reporting CBTU, which is a good identifier for good old parallel
SCSI that most of our SCSI code still is assuming.

That will change one day ...

Regards,
-- 
Kurt Garloff                   <kurt@garloff.de>         [Eindhoven, NL]
Physics: Plasma simulations    <K.Garloff@TUE.NL>     [TU Eindhoven, NL]
Linux: SCSI, Security          <garloff@suse.de>    [SuSE Nuernberg, DE]
 (See mail header or public key servers for PGP2 and GPG public keys.)



----- End forwarded message -----

-- 
Kurt Garloff                   <kurt@garloff.de>         [Eindhoven, NL]
Physics: Plasma simulations    <K.Garloff@TUE.NL>     [TU Eindhoven, NL]
Linux: SCSI, Security          <garloff@suse.de>    [SuSE Nuernberg, DE]
 (See mail header or public key servers for PGP2 and GPG public keys.)

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Re: [garloff@suse.de: Re: [linux-usb-devel] Re: /proc/scsi/map]

[James Bottomley]

kurt@garloff.de said:
> This may work for your disks. You just can't open the device node for
> a tape, if there is no medium inserted. If you know the mapping
> between to a sg device you can use it.

Actually, you have to use sg for a disc as well since you send a scsi CDB 
directly to the device for inquiry page 0x83.

> That's the second piece of information that /proc/scsi/map provides. 

Oh no question.  The way the current code doing this works is that it opens 
all scsi devices and issues a GET_IDLUN to compile a database of the nodes and 
then matches them up to sg nodes.

James