From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aaro Koskinen Subject: Re: [PATCH] sym53c8xx_2: Keep transfer negotiations valid (2.6.27.5) Date: Wed, 07 Jan 2009 15:19:57 +0200 Message-ID: <4964ABFD.9000807@nokia.com> References: <49593940.9060102@cybernetics.com> <1230631843-16470-1-git-send-email-Aaro.Koskinen@nokia.com> <1230664572.18627.2.camel@localhost.localdomain> <4963B842.9080304@cybernetics.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtp.nokia.com ([192.100.105.134]:29555 "EHLO mgw-mx09.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757039AbZAGNUo (ORCPT ); Wed, 7 Jan 2009 08:20:44 -0500 In-Reply-To: <4963B842.9080304@cybernetics.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: ext Tony Battersby Cc: James Bottomley , linux-scsi@vger.kernel.org, michaelc@cs.wisc.edu Hello, ext Tony Battersby wrote: > On a device that negotiates asynchronous, this patch causes a WDTR > exchange on every command (not just inquiry/request sense), even on > devices that don't advertise wide support in the inquiry data. This is > unnecessary overhead, and may (in theory) cause problems for old devices > that don't handle WDTR correctly. Yes, this is overlooked in the patch. Also if there is no synch nego or WDTR is rejected, then check_nego flag will stay on forever. > This patch forces either WDTR or PPR on every inquiry and request > sense. I think it would be better if the negotiation was skipped if the > current agreement and the goal are both narrow/asynchronous; that way we > don't try to negotiate at all for devices that don't support wide or sync. [...] > However, if the current agreement is 8-bit narrow and only the sync > parameters need to be renegotiated, then I think it would be better to > use SDTR only. That way we don't rely on WDTR working in order to use > SDTR successfully. These are both valid points. I will update the patch. A.