Date: Tue, 2 Dec 2008 17:18:20 -0500 From: John Baldwin <jhb@freebsd.org> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: svn-src-head@freebsd.org, Luigi Rizzo <luigi@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org Subject: Re: svn commit: r185562 - head/sys/boot/i386/boot0 Message-ID: <200812021718.20571.jhb@freebsd.org> In-Reply-To: <20081202214821.GA65840@onelab2.iet.unipi.it> References: <200812021457.mB2Evmha063418@svn.freebsd.org> <200812021425.00173.jhb@freebsd.org> <20081202214821.GA65840@onelab2.iet.unipi.it>
next in thread | previous in thread | raw e-mail | index | archive | help
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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200812021718.20571.jhb>