From owner-svn-src-head@FreeBSD.ORG Tue Dec 2 22:33:02 2008 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C8872106568D; Tue, 2 Dec 2008 22:33:02 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from server.baldwin.cx (bigknife-pt.tunnel.tserv9.chi1.ipv6.he.net [IPv6:2001:470:1f10:75::2]) by mx1.freebsd.org (Postfix) with ESMTP id 427A18FC17; Tue, 2 Dec 2008 22:33:02 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from localhost.corp.yahoo.com (john@localhost [IPv6:::1]) (authenticated bits=0) by server.baldwin.cx (8.14.3/8.14.3) with ESMTP id mB2MWoEG011992; Tue, 2 Dec 2008 17:32:56 -0500 (EST) (envelope-from jhb@freebsd.org) From: John Baldwin To: Luigi Rizzo Date: Tue, 2 Dec 2008 17:18:20 -0500 User-Agent: KMail/1.9.7 References: <200812021457.mB2Evmha063418@svn.freebsd.org> <200812021425.00173.jhb@freebsd.org> <20081202214821.GA65840@onelab2.iet.unipi.it> In-Reply-To: <20081202214821.GA65840@onelab2.iet.unipi.it> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200812021718.20571.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH authentication, not delayed by milter-greylist-2.0.2 (server.baldwin.cx [IPv6:::1]); Tue, 02 Dec 2008 17:32:56 -0500 (EST) X-Virus-Scanned: ClamAV 0.93.1/8713/Tue Dec 2 14:59:31 2008 on server.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-2.6 required=4.2 tests=AWL,BAYES_00,NO_RELAYS autolearn=ham version=3.1.3 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on server.baldwin.cx Cc: svn-src-head@freebsd.org, Luigi Rizzo , src-committers@freebsd.org, svn-src-all@freebsd.org Subject: Re: svn commit: r185562 - head/sys/boot/i386/boot0 X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 02 Dec 2008 22:33:03 -0000 On Tuesday 02 December 2008 04:48:21 pm Luigi Rizzo wrote: > On Tue, Dec 02, 2008 at 02:24:58PM -0500, John Baldwin wrote: > > On Tuesday 02 December 2008 09:57:48 am Luigi Rizzo wrote: > ... > > > + a drive number of 0x00 (floppy, or USB in floppy emulation) is > > > now accepted as valid. Previously, it was overridden with 0x80, > > > meaning that the partition table coming from the media was > > > used to access sectors on a possibly different media. > > > You can revert to the previous mode building with -DCHECK_DRIVE, > > > and you can always use the 'setdrv' option in boot0cfg > > > > I would flip this back to the original default. This was there to workaround > > certain broken BIOSes that incorrectly specified a drive of 0x00 when you > > booted from the hard drive (at least according to the comments). On such > > i don't have strong opinions on this, but i would really like to see some > evidence on how relevant the original logic (and the comments in the > code on broken BIOSes) are nowadays. That code dates back to 1998. > > On the contrary, I can point to a very current and widespread case with > AMI Bioses which, in the "Auto" emulation mode for USB device, use %dl=0 > for devices under 500MB or so; in this case the original boot0 did > the wrong thing, because overriding with 0x80 causes reading from the > wrong device. > > Granted, boot0cfg options can fix things for both cases. It's all a > matter of what is the most reasonable default. Agreed. I'm just very hesitant about changing the defaults of boot0 (or any of the boot code for that matter). -- John Baldwin