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

edward wandasiewicz 0.w3ntd at gmail.com
Tue Oct 6 14:40:05 CEST 2015


On Tue, Oct 6, 2015 at 2:02 AM, Kevin O'Connor <kevin at koconnor.net> wrote:
> 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?

Correct.

Link - Arch Linux, *BSD and Memtest86+ from the Arch Linux install ISO
all boot fine

Samus - Arch Linux boots, *BSD and Memtest86+ fail to boot, all
current snapshots as of October 2015

OpenBSD and FreeBSD do not display any dmesg output at all

NetBSD has a VESA framebuffer console which will boot, and display
dmesg output, but crashes midway - can't find disks properly

> vesa list
> vesa 1280 x 850 x 16
> boot

We see dmesg output on the screen change resolution to a (very) small
font and start it's output

>
> [...]
>> 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.

Correct. I installed the ROM from John Lewis about 2 weeks ago.

>
> 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.  :-(

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.



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