Date: Wed, 14 Sep 2005 10:13:07 -0700
From: Patrick Mansfield <patmans@us.ibm.com>
To: Luben Tuikov <luben_tuikov@adaptec.com>
Cc: Douglas Gilbert <dougg@torque.net>,
       James Bottomley <James.Bottomley@SteelEye.com>, ltuikov@yahoo.com,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       SCSI Mailing List <linux-scsi@vger.kernel.org>
Subject: Re: [PATCH 2.6.13 5/14] sas-class: sas_discover.c Discover process (end devices)
Message-ID: <20050914171307.GA10044@us.ibm.com>
References: <20050910024454.20602.qmail@web51613.mail.yahoo.com> <1126368081.4813.46.camel@mulgrave> <4325997D.3050103@adaptec.com> <20050912162739.GA11455@us.ibm.com> <4326964B.9010503@torque.net> <20050913224215.GB1308@us.ibm.com> <4328176D.80307@adaptec.com>
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On Wed, Sep 14, 2005 at 08:28:29AM -0400, Luben Tuikov wrote:
> On 09/13/05 18:42, Patrick Mansfield wrote:

> > What I mean is that the target has to intercept the command whether it is
> > a REPORT LUN or for the well known (W_LUN).
> > 
> > The target (firmware) code has to have code today like:
> > 
> > 	if (cmd == REPORT_LUN) {
> > 		do_report_lun();
> > 	}
> > 
> > For only W_LUN support, the code might be something like:
> > 
> > 	if (lun == W_LUN) {
> > 		if (cmd == REPORT_LUN) {
> > 			do_report_lun();
> > 		}
> > 	}
> > 
> > But the first case above already covers even the W_LUN case.
> 
> _Except_, that what the firmware actually does is, it routes
> the tasks by LUN first, _before_ looking up with what the command
> is.*  This is crucial.

That is what the second code snippet above is meant to show.

> > So adding a W_LUN at this point does not add any value ... maybe it looks
> > nice in the spec and in someones firmware, but it does not add anything
> > that I can see.
> 
> I wonder if the maintainer of the SCSI Core would listen or ignore your
> opinion here.

> I wonder _who_ decides here where speculation ends and industry
> opinion starts?

I am talking about the scsi spec, not the code. IMO linux scsi code should
support W_LUN and 64 bit LUN.

-- Patrick Mansfield
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