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Date:      Fri, 13 Dec 2002 08:04:12 -0800
From:      Terry Lambert <tlambert2@mindspring.com>
To:        "Ronald G. Minnich" <rminnich@lanl.gov>
Cc:        hackers@freebsd.org
Subject:   Re: [FAQ] The Open Source Stackable PC BIOS (fwd)
Message-ID:  <3DFA04FC.74881767@mindspring.com>
References:  <Pine.LNX.4.44.0212121238370.18899-100000@carotid.ccs.lanl.gov>

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"Ronald G. Minnich" wrote:
> On Thu, 12 Dec 2002, Terry Lambert wrote:
> 
> > I guess it's not OK to make BIOS calls into the BIOS?
> 
> not if it's my lazy bios that doesn't support them.

Actually, the interesting part would be a survey of which BIOS
calls are actually used (a survey by a BIOS writer, maybe, hint
hint 8-)).

The real question is fail-safe on unimplemented BIOS calls,
which should return a characteristic error.

Some BIOS calls will be required, no matter what, and they will
end up being "must implement" for you (sorry).  Others probably
need a more graceful fallback (the memory BIOS issues recently,
to accomodate some Japanese machines, mean there's a preference
for antique BIOS calls with memory, because the Japanese machines
BIOSes failed to implement failure indication correctly; have to
avoid that type of crap, if possible...).  


> > Isn't that what BIOS's are for?!?
> 
> agreed, but I was hoping that we could move beyond this bios stuff. Can't
> we all just get along :-)

The real problem here is that certain functionality was shoved
into the BIOS to make it harder for non-Microsoft OS's and
non-Intel hardware to work properly: ACPI, default card state
after POST, card features, etc..

That basically means that we get to live with the fact that the
OS has to rely on the ability to make BIOS calls, since there is
no equivalent data map for the configuration state that could be
used to implement via non-BIOS code.

That doesn't mean you have to implement it in your reduced BIOS,
but it does mean that you have to implement proper indication of
failures, when calls you don't implement are used (again, sorry).

-- Terry

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