Task tags in SRP

Gibson, Chuck Chuck_Gibson at adaptec.com
Tue Feb 5 12:45:35 PST 2002


* From the T10 Reflector (t10 at t10.org), posted by:
* "Gibson, Chuck" <Chuck_Gibson at adaptec.com>
*
Hi John,

The task tag is chosen by the host (initiator).  It is considered opaque to
an I/O controller,
and is just returned to the host on an I/O completion so the host can
associate a completed
I/O with whatever context it is maintaining for the command.  Some hosts use
the address of a
particular data structure related to the command as the tag value.
In the case of a Task Management Request, there are two tags of note.  The
first one, starting
at offset 8 in the request, is the tag of the Task Mgmt request itself.  The
second one, starting
at offset 32, is the (previously issued) tag of the specific task that the
Task Management Request
is targeted at. Also worth noting - SRP doesn't require the target to check
the value of tags for
duplication.  That is also a host responsibility.

Regards,

________________
Chuck Gibson
Principal Engineer
Corporate Technology Group
Adaptec, Inc.
(408) 957-2084
cgibson at corp.adaptec.com


-----Original Message-----
From: John Middleton [mailto:jmiddleton at banderacom.com]
Sent: Tuesday, February 05, 2002 11:29 AM
To: t10 at t10.org
Subject: Task tags in SRP


* From the T10 Reflector (t10 at t10.org), posted by:
* "John Middleton" <jmiddleton at banderacom.com>
*
I hope there isn't too obvious an answer to this question...

In reviewing the SRP draft, I'm confused about the use of tags.  It appears
that each SRP request and response use an "SRP tag".  There is reference to
a Task Tag in the SRP_TSK_MGMT request, however.  I don't understand how
this tag is acquired. If someone can point me in the right direction, I'd
appreciate it.

Thanks,
John Middleton


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