From: James Bottomley <James.Bottomley@steeleye.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Joerg Schilling <schilling@fokus.fraunhofer.de>,
Matthew Dharm <mdharm-usb@one-eyed-alien.net>,
magliery@csb.yale.edu, appro@fy.chalmers.se,
USB development list <linux-usb-devel@lists.sourceforge.net>,
SCSI development list <linux-scsi@vger.kernel.org>
Subject: Re: [linux-usb-devel] FW: USB 2.0 external hard drive problem
Date: 06 Feb 2004 10:24:25 -0500 [thread overview]
Message-ID: <1076081067.1823.5.camel@mulgrave> (raw)
In-Reply-To: <Pine.LNX.4.44L0.0402060946350.830-100000@ida.rowland.org>
On Fri, 2004-02-06 at 09:59, Alan Stern wrote:
> Who says it's wrong to retrieve sense information when there is an
> underrun but not Check Condition? Can you provide a reference to a
> published (or draft) document that states this?
It's not wrong according to the SCSI standards, a REQUEST SENSE issued
to a device with no sense data will produce a NO SENSE key.
However, because of the way sense is processed in contingent allegiance
conditions (suspending the I_T_L nexus until sense is cleared) it is
dangerous to issue arbitrary request sense commands because you may
receive sense for a different command (and prevent that command from
erroring correctly).
The SCSI mid-layer definitely does not expect this behaviour. A driver
either does not do any sense commands at all or it only issues a REQUEST
SENSE in response to a Check Condition status in order not to have the
nexus halted because of a contingent allegiance condition (simulating
ACA if you will).
James
next prev parent reply other threads:[~2004-02-06 15:24 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200402061211.i16CBSIw001678@burner.fokus.fraunhofer.de>
2004-02-06 14:59 ` [linux-usb-devel] FW: USB 2.0 external hard drive problem Alan Stern
2004-02-06 15:24 ` James Bottomley [this message]
2004-02-06 20:59 ` Matthew Dharm
2004-02-09 16:40 ` Alan Stern
2004-02-09 16:50 ` James Bottomley
2004-02-09 21:11 ` Matthew Dharm
2004-02-09 21:30 ` Alan Stern
2004-02-09 22:11 ` Tony Battersby
2004-02-06 15:10 Joerg Schilling
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