From: Matthew Wilcox <willy@linux.intel.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Sarah Sharp <sarah.a.sharp@linux.intel.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-usb@vger.kernel.org, linux-scsi@vger.kernel.org,
USB Storage List <usb-storage@lists.one-eyed-alien.net>
Subject: Re: [usb-storage] Re: Make UAS work on HS for devices with and without command tagging support
Date: Mon, 19 Dec 2011 15:57:37 -0500 [thread overview]
Message-ID: <20111219205737.GR14291@linux.intel.com> (raw)
In-Reply-To: <1324326458.5123.14.camel@dabdike.int.hansenpartnership.com>
On Mon, Dec 19, 2011 at 02:27:38PM -0600, James Bottomley wrote:
> Hm, OK, that was actually something added to SAM-4. It's not present in
> SAM-3. However, it does look like SAS always tried to get away with
> this, notably by deciding in SAS-1 (which was SAM-3 based) that the
> Frame tag wasn't the same thing as a SAM-3 Q.
So ... T10 have put us in a bit of an awkward position here; by solving
a problem that didn't need to be solved, they've created a new problem.
We're sending a packet stream that's permitted by SAS-1 standards and not
by SAS-2 standards (but probably isn't going to be checked by any device).
To be technically correct, we've got to use shared tag maps (with the
extra locking overhead) for any device that claims to be SAS-2 compliant.
That's ... complex.
So are we just going to pretend that T10 never made this change? :-)
next prev parent reply other threads:[~2011-12-19 20:57 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-14 18:47 Make UAS work on HS for devices with and without command tagging support Sebastian Andrzej Siewior
2011-12-14 18:47 ` [PATCH 1/2] usb/uas: fix support on HS (device without command tagging) Sebastian Andrzej Siewior
[not found] ` <1323888472-21035-2-git-send-email-bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2011-12-15 11:14 ` Sergei Shtylyov
2011-12-14 18:47 ` [PATCH 2/2] usb/uas: fix support on HS (device with " Sebastian Andrzej Siewior
2011-12-14 22:53 ` Make UAS work on HS for devices with and without command tagging support Sarah Sharp
2011-12-15 8:44 ` Sebastian Andrzej Siewior
[not found] ` <4EE9B375.4020606-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2011-12-15 21:12 ` [usb-storage] " Sarah Sharp
2011-12-16 14:47 ` Sebastian Andrzej Siewior
2011-12-16 20:12 ` Sebastian Andrzej Siewior
2011-12-16 20:31 ` Matthew Wilcox
2011-12-16 20:42 ` Sebastian Andrzej Siewior
2011-12-16 21:36 ` Sarah Sharp
2011-12-16 21:44 ` Alan Stern
2011-12-16 21:47 ` James Bottomley
2011-12-19 16:12 ` Matthew Wilcox
2011-12-19 17:14 ` James Bottomley
2011-12-19 18:36 ` Matthew Wilcox
2011-12-19 20:27 ` James Bottomley
2011-12-19 20:57 ` Matthew Wilcox [this message]
2011-12-19 21:22 ` James Bottomley
2011-12-19 16:14 ` [PATCH] usb/uas: use unique tags for all LUNs Sebastian Andrzej Siewior
2011-12-19 19:39 ` [PATCH] usb/uas: use scsi_host_find_tag() to find command from a tag Sebastian Andrzej Siewior
[not found] ` <20111219193955.GA2060-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
2011-12-19 19:50 ` Matthew Wilcox
2011-12-19 20:12 ` Sarah Sharp
2011-12-19 21:01 ` Matthew Wilcox
2011-12-16 20:51 ` [usb-storage] Re: Make UAS work on HS for devices with and without command tagging support Sarah Sharp
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