From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH 1/1] pata_it821x: fix lost interrupt with atapi devices Date: Mon, 17 Sep 2007 06:00:19 -0400 Message-ID: <46EE5033.7060708@garzik.org> References: <200709041607.l84G7KsT032647@norden.math.tntech.edu> <18141.42848.537873.349518@alkaid.it.uu.se> <20070906013929.1621849d@the-village.bc.nu> <46EE09D3.9010201@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:59473 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753115AbXIQKAe (ORCPT ); Mon, 17 Sep 2007 06:00:34 -0400 In-Reply-To: <46EE09D3.9010201@gmail.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo Cc: Alan Cox , Mikael Pettersson , Jeff Norden , alan@redhat.com, linux-kernel@vger.kernel.org, Albert CC Lee , IDE/ATA development list Tejun Heo wrote: > [cc'ing Albert and linux-ide] > > Alan Cox wrote: >> /from the media. */ >>> > + if (qc->nbytes < 2048) >>> > + return -EOPNOTSUPP; >>> > + >>> > /* No ATAPI DMA in smart mode */ >>> > if (itdev->smart) >>> > return -EOPNOTSUPP; >>> > >>> >>> This looks like a gross hack. Aren't you supposed to inspect >>> the command instead and whitelist the ones you know are OK, >>> like pata_pdc2027x.c and sata_promise.c do? >> It does seem to be about transfer size in the IT821x case not commands. >> It may be to do with how we issue ATAPI command transfer sizes from high >> up (patch went to Jeff) but for now this is definitely the right approach >> >> Reviewed-by: Alan Cox > > I wonder whether we should be using similar check in generic path too. > We have quite a few cases where MWDMA ATAPI devices choking on commands > with small transfer sizes. I don't think we'll experience significant > performance regression with this applied and even if there is some, it's > far better to have slightly slower working device. > > What do you guys think? Need to look at, or know, a standard profile of submitted commands. It's quite possible some high performance commands want this, where possible. Jeff