[LinuxBIOS] V3 fallback, failover, and the normal boot flag.

Peter Stuge peter at stuge.se
Wed Jul 18 17:32:02 CEST 2007

On Wed, Jul 18, 2007 at 01:15:50PM +0200, Stefan Reinauer wrote:
> * Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006 at gmx.net> [070718 12:43]:
> > Hm. Can we abuse ACPI to do that? Like accessing SystemCMOS from a
> > _INI function?
> Possibly. But ACPI is running very early in the game. Where would we
> hook it up?
> This would also establish ACPI as a pretty hard requirement. There
> should be an alternative, too.
> Using ACPI here would be nicely transparent though, hiding firmware
> specifics in the firmware code. I like that approach.

We want to use less ACPI, not more, right?
Tempting as it may be, can't we find a better way?

On Wed, Jul 18, 2007 at 04:13:24PM +0200, Carl-Daniel Hailfinger wrote:
> http://www.microsoft.com/whdc/resources/respec/specs/simp_bios.mspx
> For the real spec, see
> http://www.microsoft.com/whdc/resources/respec/specs/simp_boot.mspx
> or google for "sbf21.doc". I have not read the real spec because I
> didn't want to agree to their LA.

Also see Dell's patent:


or just google simple boot flag. This article is informative:


It seems that the simple boot flag is merely intended to control what
parts of POST is performed. Not a perfect fit for us..

> Since I just discovered the Microsoft approach, I doubt we would
> want to invent our own mechanism.

But they are two different problems.

We could use the simple boot flag to do clever things during init
(like cache a list of register writes) but normal vs. fallback is
AFAIK a new concept at least in PC firmware so there's no existing
mechanism that really fits.


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