From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 1/1] pata_it821x: fix lost interrupt with atapi devices Date: Mon, 17 Sep 2007 07:00:03 +0200 Message-ID: <46EE09D3.9010201@gmail.com> References: <200709041607.l84G7KsT032647@norden.math.tntech.edu> <18141.42848.537873.349518@alkaid.it.uu.se> <20070906013929.1621849d@the-village.bc.nu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from wa-out-1112.google.com ([209.85.146.182]:55894 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752558AbXIQI07 (ORCPT ); Mon, 17 Sep 2007 04:26:59 -0400 Received: by wa-out-1112.google.com with SMTP id v27so1953884wah for ; Mon, 17 Sep 2007 01:26:58 -0700 (PDT) In-Reply-To: <20070906013929.1621849d@the-village.bc.nu> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Alan Cox Cc: Mikael Pettersson , Jeff Norden , alan@redhat.com, linux-kernel@vger.kernel.org, Albert CC Lee , IDE/ATA development list [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? -- tejun