i386/100831: sio ignores BIOS information about serial ports - bounty offered

Jo Rhett jrhett at svcolo.com
Wed Aug 2 21:50:23 UTC 2006

The following reply was made to PR i386/100831; it has been noted by GNATS.

From: Jo Rhett <jrhett at svcolo.com>
To: Bruce Evans <bde at zeta.org.au>
Cc: freebsd-gnats-submit at freebsd.org, freebsd-i386 at freebsd.org,
        njl at freebsd.org
Subject: Re: i386/100831: sio ignores BIOS information about serial ports - bounty offered
Date: Wed, 2 Aug 2006 14:42:43 -0700

 On Thu, Aug 03, 2006 at 05:32:35AM +1000, Bruce Evans wrote:
 > I don't completely understand this either.  I think there is a non-ACPI part
 > of the BIOS that FreeBSD (or all OS's doesn't see).  As I understand your
 > configuration, you start with COM1 and COM2 at the usual places but don't
 > want to use COM1 so you change the BIOS settings for COM2 to the usual ones
 > for COM1 and maybe vice versa.  This changes soft jumpers or whatever is
 > needed for FreeBSD to see it.  Then you use a BIOS option to swap the ports
 > so that everything is supposed to see COM2 as COM1.  The boot loader sees
 > this but ACPI in FreeBSD doesn't.  I think this changes is only made in
 > some BIOS table that ACPI in FreeBSD doesn't know about.  In my test, I
 > only swapped the settings of COM1 and COM2 in the BIOS, since I couldn't
 > find a BIOS option to swap the unit number assignments, so it was not
 > completely incorrect for ACPI in FreeBSD to swap the settings.
 Huh?  I separated this to make it clear.
 You can't make COM1 be COM2.  What you're saying is nonsense. 
 (not an insult, it just doesn't make sense)
 There are two serial ports: A and B.  I can assign 03f8 irq 4 to either of
 them, and 02f8 irq 3 to the other.  (or com3 or com4 doesn't matter)
 FreeBSD is currently assigning sio0 to serial A, regardless of the IO and
 IRQ settings.  Likewise sio1 to Serial B, regardless of configuration.  It
 appears likely that they are assigned based entirely on the order that they
 are presented via ACPI, and device hints are ignored entirely.
 However, the boot loader console does use device hints and does work 
 Jo Rhett
 senior geek
 SVcolo : Silicon Valley Colocation

More information about the freebsd-i386 mailing list