[SeaBIOS] VGA Option ROM not set up correctly when loaded by coreboot and not SeaBIOS

[Kevin O'Connor]

On Wed, Mar 20, 2013 at 01:21:48AM +0100, Paul Menzel wrote:
> To summarize, I have to figure out if coreboot is able to run the VGA
> option ROM correctly and if yes, why SeaBIOS, GRUB and Linux cannot
> use(?) it.

If you want to use the option ROM during runtime, then SeaBIOS (and
only SeaBIOS) should run the option ROM.  Nothing else will work
reliably.

SeaBIOS needs to run the rom, because otherwise the 16bit runtime
hooks that the option ROM establishes will not be present during
runtime.

Running the option ROM in both coreboot and SeaBIOS is not desirable,
because option ROMs are not designed to initialize the hardware twice
- it could easily get confused.

So, why does coreboot even have the ability to run option ROMs?  This
feature is useful when not using SeaBIOS, as it allows coreboot to
initialize the VGA hardware.  Some programs can talk directly to the
vga hardware, but only if the vga hardware has been initialized.  This
doesn't work for anything that talks to the vga hardware via the VGA
option ROM - all of these users must use SeaBIOS and must let SeaBIOS
run the option ROM.

-Kevin