From owner-freebsd-current@FreeBSD.ORG Fri Jul 30 19:48:06 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 2D33E16A4CE for ; Fri, 30 Jul 2004 19:48:06 +0000 (GMT) Received: from out003.verizon.net (out003pub.verizon.net [206.46.170.103]) by mx1.FreeBSD.org (Postfix) with ESMTP id C889443D6B for ; Fri, 30 Jul 2004 19:48:05 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from [192.168.1.3] ([68.161.100.95]) by out003.verizon.net (InterMail vM.5.01.06.06 201-253-122-130-106-20030910) with ESMTP id <20040730194648.MOTN26805.out003.verizon.net@[192.168.1.3]>; Fri, 30 Jul 2004 14:46:48 -0500 Message-ID: <410AA5A5.4000001@mac.com> Date: Fri, 30 Jul 2004 15:46:45 -0400 From: Chuck Swiger Organization: The Courts of Chaos User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.1) Gecko/20040707 X-Accept-Language: en-us, en MIME-Version: 1.0 To: =?ISO-8859-1?Q?S=F8ren_Schmidt?= References: <410A3833.7030502@portaone.com> <410A47C7.1080808@DeepCore.dk> <410A9B58.8000502@mac.com> <410A9D77.4030703@DeepCore.dk> In-Reply-To: <410A9D77.4030703@DeepCore.dk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Authentication-Info: Submitted using SMTP AUTH at out003.verizon.net from [68.161.100.95] at Fri, 30 Jul 2004 14:46:48 -0500 cc: Maxim Sobolev cc: current@freebsd.org Subject: Re: Is there still sufficient reason for hw.ata.atapi_dma being 0 by default? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 30 Jul 2004 19:48:06 -0000 Søren Schmidt wrote: > Chuck Swiger wrote: [ ... ] >> Before CD burners became common, having this sysctl default to zero >> was almost entirely harmless: people would simply read from CD-ROM >> drives slower than optimal. If we change the default to one, people >> with fast burners will no longer generate coasters by default too. In >> other words, Maxim has provided a pretty good reason for changing the >> default of atapi_dma, I think. :-) > > Actually not, most if not all modern fast burners implements some sort > of "burn proof" ie no coasters at all due to buffer underruns... You're right that truly modern fast burners ought to implement "justlink" or "burn proof". However, I don't think it's a good idea to depend on the burner to be able to handle underruns; I'd rather run CD/DVD burners using UDMA. [ FWIW, I've got a 16/10/40x Yamaha burner which just predates the first generation of burners with underrun protection-- this affects me directly. ] [ ... ] >> ...which will switch a device generating errors from UDMA mode to >> PIO? Can this check also turn off using atapi_dma (if using PIO >> doesn't already imply not using DMA)? > > Not really, the problem with ATAPI dma is that if it fails it most > likely locks up the machine, so there is no way to back pedal... Oh. Ewww. Could chipsets which do that be added to a "quirks" table similar to the way USB devices are being handled? Or is it not just the chipset, but some more complex interaction between ATAPI DMA and other devices in the system which want to do DMA which causes the lockup? -- -Chuck