From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262329AbUHJImA (ORCPT ); Tue, 10 Aug 2004 04:42:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262279AbUHJImA (ORCPT ); Tue, 10 Aug 2004 04:42:00 -0400 Received: from mail.dt.e-technik.Uni-Dortmund.DE ([129.217.163.1]:31122 "EHLO mail.dt.e-technik.uni-dortmund.de") by vger.kernel.org with ESMTP id S262138AbUHJIl6 (ORCPT ); Tue, 10 Aug 2004 04:41:58 -0400 Date: Tue, 10 Aug 2004 10:41:59 +0200 From: Matthias Andree To: Jens Axboe Cc: Joerg Schilling , linux-kernel@vger.kernel.org Subject: Re: PATCH: cdrecord: avoiding scsi device numbering for ide devices Message-ID: <20040810084159.GD10361@merlin.emma.line.org> Mail-Followup-To: Jens Axboe , Joerg Schilling , linux-kernel@vger.kernel.org References: <200408061330.i76DU2Tm005937@burner.fokus.fraunhofer.de> <20040806151017.GG23263@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040806151017.GG23263@suse.de> User-Agent: Mutt/1.5.6i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Jens Axboe schrieb am 2004-08-06: > On Fri, Aug 06 2004, Joerg Schilling wrote: > > Let me give you a short answer: If DMA creates so many problem on Linux, > > how about imlementing a generic DMA abstraction layer like Solaris does? > > We do have that. But suddenly changing the alignment and length > restrictions on issuing dma to a device in the _end_ of a stable series > does not exactly fill me with joyful expectations. It's simply that, > not lack of infrastructure. The problem has been reported again and again throughout the whole 2.4 cycle and has grown ever more painful as devices became faster. It's not exactly fun if everything can do 48X but your favorite OS (Linux 2.4) is limited to say 8X because it only does PIO in spite of hdparm settings and everything else. I didn't care much because I had a SCSI writer at that time which had working DMA (and was also slow...) but as that turned out to become unreliable, I bought one of the nice Plextors and now was faced with the problem I couldn't use it at full speed. FreeBSD came to the rescue while 2.6 started to become stable through its early releases. It's Marcelo's call to decide if he wants the DMA addressing requirements relaxed for 2.4.28 or if 2.4 is closed. If 2.4 is now bugfixes-only then this certainly qualifies after some testing. If it doesn't work out, it can still be disabled through the -rc versions, or it can be some sysctl if you fear adverse effects. -- Matthias Andree NOTE YOU WILL NOT RECEIVE MY MAIL IF YOU'RE USING SPF! Encrypted mail welcome: my GnuPG key ID is 0x052E7D95 (PGP/MIME preferred)