Negotiation On Reselection -Reply

ASpaldin at corp.adaptec.com ASpaldin at corp.adaptec.com
Thu Mar 13 07:55:00 PST 1997


* From the SCSI Reflector (scsi at symbios.com), posted by:
* ASpaldin at corp.adaptec.com
*
Form: Reply
Header: Adaptec
Text: (21 lines follow)
Pat asked:
>Why doesn't a power-on reset - be it as
>innocuously provoked as by an 0Ch Device
>Reset message - cancel the READ command and
>keep the target from ever reselecting?

You got me - well almost. I maybe took my example too far, I should have 
stopped at  most Initiators negotiate on receipt of a Check condition (as 
you state later). However, my example is still valid as it is possible in 
certain implementations that the READ response may be already enqueued to 
the adapter H/W execution queue and may go out before some higher level 
entity interprets the Request Sense information determines that any active 
requests from the initiator must be aborted. 

Thanks for the question.

Cheers 
alan

alan spalding
email: alan_spalding at corp.adaptec.com
Original text: (37 lines follow)
>From owner-scsi at Symbios.COM, on 3/13/97 7:05 AM:
To: scsi at Symbios.COM

* From the SCSI Reflector (scsi at symbios.com), posted by:
* PAT LaVarre <LAVARRE at IOMEGA.COM>
*
> As the Check condition might imply 
> power/on reset, we need to renegotiate the
> transfer rates and perform this
> negotiation on the reselection for the
> READ command.

Fun.

Want a question from the peanut gallery
(i.e. from someone who never read anything
about the peer-to-peer capabilities)?

Why doesn't a power-on reset - be it as
innocuously provoked as by an 0Ch Device
Reset message - cancel the READ command and
keep the target from ever reselecting?

(The fact that resets kill off disconnected
stuff is part of why, for ordinary SCSI disk
drives, in vanilla environments, negotiation
occurs only as part of each op 03h Request
Sense auto-issued in response to an 02h
Check Condition status or as part of 12h
inquiry.)

Thanks in advance.   Pat LaVarre

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