Mapping Video BIOS?

Greg 'groggy' Lehey grog at
Sun Jul 27 21:02:03 PDT 2003

On Sunday, 27 July 2003 at 21:42:35 -0600, M. Warner Losh wrote:
> In message: <20030728032653.GA37499 at>
>             "Greg 'groggy' Lehey" <grog at> writes:
>> On Saturday, 26 July 2003 at 22:18:59 -0600, M. Warner Losh wrote:
>>> In message: <20030727015903.GJ45069 at>
>>>             "Greg 'groggy' Lehey" <grog at> writes:
>>>> Presuming that it's the ROM driver, I get this in the dmesg I posted:
>>>> pnpbios: Bad PnP BIOS data checksum
>>> That's likely the problem.  However, PnP BIOS information isn't the
>>> same thing that the orm[sic] driver probes for.
>> They look related.  I've now found the orm output:
>>   orm0: <Option ROMs> at iomem 0xe0000-0xe3fff,0xdf800-0xdffff,0xd0000-0xd17ff,0xc0000-0xcefff on isa0
>> The last one is the video BIOS.  It's interesting to note that it
>> doesn't report the 4 kB BIOS at 0xcf000, which suggests that at this
>> point the 16 kB area is already unmapped.
> Hmmmm, The list comes from scanning the "ISA HOLE" for certain memory
> signatures.  These signatures have a length in them that say "I'm a
> rom that's X long".

Sure.  The data at offset 0xc0000 are:

C000:0000  55 AA 78 E9 44 06 00 00-00 00 00 00 00 00 00 00   U.x.D...........

The 0xaa55 is the BIOS signature ("Here be a BIOS"), and the 0x78 is
the length byte (120 sectors, or 60 kB).  That's how orm0 knows the
end address.

> I don't think that it suggests that things are 'unmapped'...

If the area between 0xcc000 and 0xcffff had been mapped, orm0 would
have found this too:

C000:F000  55 AA 08 E8 6D 0B CB 11-FE 02 00 00 00 00 00 00   U...m...........

>> I've worked around the problem by compiling the video BIOS into the X
>> server and not trying to access the BIOS in the machine.  Obviously
>> not a solution, but it works for the moment.  I'd really like to track
>> down the problem.  Does anybody have an idea?
> I don't, I'm sorry.

Understood.  I was hoping that somebody else might have some ideas.

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