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

[Kevin O'Connor]

On Mon, Oct 05, 2015 at 05:04:09PM +0100, edward wandasiewicz wrote:
> Following on from this post - http://seabios.seabios.narkive.com/UAt3jVij
> 
> I was having the exactly the same problem.

So to summarize, you can boot Linux on Samus, but can not boot any
*BSD?  Both Linux and the BSDs do work on Link?

[...]
> If I run "vbeinfo" within Grub2 on the Pixel 2013, we get a long list,
> including 640 x 400 and 800 x 600
> 
> On the Pixel 2015, "vbeinfo" only gives one entry, and one entry only
> of 1280 x 850 x 16
> 
> Could this explain why *BSD operating systems and MemTest utility
> cannot boot from USB or SD card (..properly..) ? They boot up in a
> "text console", versus a "graphical console in text mode".

It's certainly possible that cbvga SeaVGABIOS is the cause.  The cbvga
support in SeaVGABIOS is a hack to get some minimal display support
when only a graphical framebuffer is available.  It is known to not
work with some bootloaders and OSes (that don't use the VGA BIOS to
write to the screen).  For that reason, it's not going to work with
MemTest86+.

Looks like you have a rom from John Lewis.  I'd confirm that the
SeaVGABIOS in the rom is relatively recent as there were some changes
("leal" emulation) that are known to work better on the *BSDs.

If SeaVGABIOS is recent, then I think the next step would be to see if
you can replace SeaVGABIOS with an Intel VGABIOS.

-Kevin


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.  :-(