Resource Allocation for Option Rom

Stefan Reinauer stepan at
Thu May 27 15:09:00 CEST 2004

* Eric W. Biederman <ebiederman at> [040527 22:16]:
> We could probably reserve a hole for this purpose, which
> is a good idea except for bridges. 
Also, the graphics card option roms are usually hardcoded to 0xc0000

> Be very careful here.  The PCI spec allows the option rom BAR
> to be mutually exclusive with the other BARS so in general
> they both can not be enabled.

The only safe way to go is probably to probe one after the other while
leaving the rest untouched, i.e

 1) probe option rom, if it doesn't exist go to 6.
 2) enable option rom
 3) evtl. copy rom code to ram (in case it installs an 
    int13 handler or such)
 4) execute option rom code.
 5) disable option rom
 6) repeat this for all pci devices.

This procedure should be a part of "testbios" rather than LinuxBIOS' PCI
code, but reserving some space for it early might be the way to go


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