[SeaBIOS] Problems booting legacy OSes on Chromebook Pixel 2015 - cbmem output

Kevin O'Connor kevin at koconnor.net
Tue Oct 6 17:26:49 CEST 2015


On Tue, Oct 06, 2015 at 01:40:05PM +0100, edward wandasiewicz wrote:
> On Tue, Oct 6, 2015 at 2:02 AM, Kevin O'Connor <kevin at koconnor.net> wrote:
> > P.S. it should be possible to implement a SeaVGABIOS with support for
> > mode switching on Intel graphics adapters.  That should solve these
> > problems (at least on Intel hardware), but it's a bit of work as I
> > find the Intel graphics manuals to be basically indecipherable.  :-(
> 
> Does this explain why there is only one mode available. Other
> resolutions could be added, but since there is no support for mode
> switching, we don't have the ability to change back and forth from any
> of them, even if we tried.

Right.  Also, some boot loaders (and kernels) try to write directly to
the legacy framebuffers.  With cbvga SeaVGABIOS the gpu isn't actually
using these legacy framebuffers.  As a result the video output is not
seen and it looks like a crash.  If SeaVGABIOS could instruct the gpu
to change into the legacy modes then the legacy framebuffers would
actually be valid.

-Kevin



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