From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: Polling (was Re: [PATCHSET 2/2] implement PMP support, take 6) Date: Fri, 28 Sep 2007 21:43:53 -0400 Message-ID: <46FDADD9.9050007@garzik.org> References: <1190521193410-git-send-email-htejun@gmail.com> <46F9BF3E.5050708@garzik.org> <46FA1B4E.8090103@gmail.com> <46FD079F.3010007@garzik.org> <46FD0D50.8030602@gmail.com> <46FD1C4A.8010101@garzik.org> <46FD306C.3050205@gmail.com> <46FD5DE1.8000206@rtr.ca> <20070928220309.7c9ed816@the-village.bc.nu> 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]:50210 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751996AbXI2Bn5 (ORCPT ); Fri, 28 Sep 2007 21:43:57 -0400 In-Reply-To: <20070928220309.7c9ed816@the-village.bc.nu> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Alan Cox , Mark Lord Cc: Tejun Heo , linux-ide@vger.kernel.org Alan Cox wrote: >> Jeff, seeing as Tejun's commitment is never in doubt here, >> I really believe we should go with the existing PMP patchset >> for 2.6.24 (unless the respin happens quickly enough). >> >> This functionality is way overdue, and we shouldn't be impeding it >> as long as we have been. > > I would second this. Its far too important to not get this stuff upstream > and usable NOW. Yes the model will have to change a bit but the entire > libata today has almost no resemblence to the one a year ago. > > It can evolve and then the old one can die off just as we did with EH > (except for libsas anyway) I certainly deserve plenty of blame for not catching this fact earlier, much to my chagrin. But there are real technical issues at hand: Polling ALREADY makes the job of fixing SAS/SATA exception handling difficult. Expanding polling to something SAS/SATA controllers treat as fundamentally irq-driven and integrated with the rest of the command flow is moving in the wrong direction. To re-re-re-summarize, polling in PMP is fundamentally broken for an ENTIRE CLASS OF HARDWARE that we actively support today. And jgarzik/misc-2.6.git#sas is adding two more controllers to that list. Jeff