SPI-4 Negotiation Message Rewrite Comment

Elliott, Robert Robert.Elliott at COMPAQ.com
Fri Jul 27 11:44:55 PDT 2001

* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert" <Robert.Elliott at compaq.com>
> * From the T10 Reflector (t10 at t10.org), posted by:
> * "Kendall, Guy" <gkendall at lsil.com>
> *
> I have been reviewing T10/01-131r2 and have one minor 
> comment. In section 4.1.3, it lists the cases where an 
> initiator shall consider its transfer agreement invalid. 
> Item b) is a unit attention with an ASC of 29h. I believe
> that the note in this section is incorrect. The note states:
> "These additional sense codes are never reported in a status 
> information unit because SCSI devices default to 
> information units disabled"
> I would suggest that this note be removed because these codes 
> actually can be reported in a status IU. It just depends on the 
> order in which the initiator negotiates to enable information 
> units, versus when it sends a CDB that will generate a unit 
> attention condition. INQUIRY, REPORT LUNS, and REQUEST SENSE 
> typically don't generate unit attentions so a negotiation
> enabling information units could happen on those commands, 
> followed by a TEST UNIT READY which does generate a unit 
> attention condition. In this case information units are 
> enabled when the TEST UNIT READY generates a unit
> attention and the sense data will come back in a Status IU.
> Guy Kendall
> LSI Logic

Good point.  The note has to go.

The initiator port need not consider its transfer agreement invalid if the
unit attention status is communicated via a status information unit, because
the agreement must be valid for the IU to work.

There are two cases:
1) initiator port was speaking IU mode; hot plug occurs; unexpected COMMAND
phase occurs. Case c) already lists that this indicates the transfer
agreement is invalid.  Once negotiation is done, the agreement can still be
considered valid even if a unit attention occurs.  Another hot plug could
occur while in non-IU mode before the unit attention is reported, but
target-originated negotiation should cover that case.

2) initiator port was speaking non-IU mode; hot plug occurs; initiator port
chooses to enable IU mode on an INQUIRY, REPORT LUNS, or REQUEST SENSE; then
the unit attention is reported on another command.  In this situation the
transfer agreement need not be considered invalid. 

Should we try to express this in standardese or just mandate extra
negotiations after every such unit attention, even in the case where it is
not strictly required?

Rob Elliott, Compaq Server Storage
Robert.Elliott at compaq.com

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