INQUIRY question

Robert Griswold rgriswold at crossroads.com
Tue Aug 7 11:29:41 PDT 2001


* From the T10 Reflector (t10 at t10.org), posted by:
* "Robert Griswold" <rgriswold at crossroads.com>
*
Jim:

It seems that given the wording of SPC-2, it all becomes dependant on
the device server implementation, specifically to the parsing of the
received CDB.  If the target verifies that the LUN does not exist first,
it may disqualify all other responses (including CHECK CONDITION) in
favor of returning the 'invalid' device qualifiers, but if it also
checks the consistency of the EVPD and CmdDt fields, it may also deliver
the CHECK CONDITION along with the 7F.  As a target implementation, I
believe I would favor sending the 7F qualifier over the CHECK CONDITION
(irrespective of the other bits), leaving the standard Inquiry data
in-tact as specific to LUN 0 for the target, since there is no direct
CHECK CONDITION directive for that condition.

As an initiator (scanning LUNs on a selected target, for instance) I
would probably ignore all fields (except for the 7F) in such a
situation, and probably even ignore the check condition since the LUN
doesn't exist.

Bob

Robert Griswold
Technologist
Crossroads Systems, Inc.
512-928-7272

 -----Original Message-----
From: 	Jim Hafner [mailto:hafner at almaden.ibm.com] 
Sent:	Friday, August 03, 2001 10:35 AM
To:	t10 at t10.org
Subject:	INQUIRY question

* From the T10 Reflector (t10 at t10.org), posted by:
* "Jim Hafner" <hafner at almaden.ibm.com>
*
Folks,

Here's an edge case that I don't think is clearly specified in SPC-2
(but
please prove me wrong).

Suppose a device gets an INQUIRY Command to an unsupported LUN value.
The
spec says that the device has to respond with standard inquiry data with
the first byte set to 7F ("there's nothing there").  That's presuming
that
EVPD=CmdDt=0. It doesn't say what meaning or values go in the rest of
the
fields of the response (shouldn't it say that the rest of the fields can
be
anything and should be ignored by the initiator?).  It also isn't clear
what happens when the EVPD bit is set to 1 and the page code is a
mandatory
one.   Should it still return garbage data? Can it return CHECK
CONDITION
in this case?

Any guidance?

Jim Hafner

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