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Date:      Tue, 02 Jun 1998 17:13:05 -0400 (EDT)
From:      Simon Shapiro <shimon@simon-shapiro.org>
To:        Mike Smith <mike@smith.net.au>
Cc:        "freebsd-scsi@freebsd.org" <freebsd-scsi@FreeBSD.ORG>, "freebsd-current@freebsd.org" <freebsd-current@FreeBSD.ORG>
Subject:   Re: DPT Redux
Message-ID:  <XFMail.980602171305.shimon@simon-shapiro.org>
In-Reply-To: <199806021707.KAA00985@antipodes.cdrom.com>

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I am deleting the cross-post to current....

On 02-Jun-98 Mike Smith wrote:
 ...

> Then could you characterise "returning a successful completion code for 
> an incomplete/failed transfer"?  The SCSI stack has to assume at this 
> point that the transaction is complete, even though you're admitting 
> that it's not.

There was one specific failure mode, yes.  To get there, especially on a
RAID array, you had to have so many ducks lined up:

*  DPT free enough to accept commands
*  DPT so busy it will not reply to INQUIRY on a RAID array (there is no
   SCSI bus involved here)
*  DPT not setting the hardware registers as busy, while oh, so busy.

This condition had to persist for several minutes.  The patch checked in
against current fixes that.  the same patch will/should be checked in
against 2.2 any moment now.

BTW, for this to exist, the DPT firmware has to be rather sick.  I can
rplicate this scsnario with some broken, unpublished versions of the
firmware.

Simon


---


Sincerely Yours, 

Simon Shapiro                                           Shimon@Simon-Shapiro.ORG
                                                        770.265.7340

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