[coreboot] SeaBIOS and the Geode LX framebuffer

Stephen Crocker scrocker at ampltd.com
Mon Oct 6 17:24:24 CEST 2008

Jordan Crouse wrote:
> On 06/10/08 15:31 +0100, Stephen Crocker wrote:
>> Carl-Daniel Hailfinger wrote:
>>> On 03.10.2008 12:29, Stephen Crocker wrote:
>>>> Is there a way of getting VGA support with SeaBIOS on the AMD Geode LX
>>>> framebuffer?  I have successfully built and tested a BIOS image that
>>>> appears to boot into DOS but the lack of display means that it is of
>>>> little use.  Is there a VGA ROM image that I can include?
>>> You'd need a VGA emulation VSA and AFAIK that piece of software is not
>>> available as open source due to an interesting rights situation.
>> How much of this is handled in AMD's binary VSA module?  I have been 
>> looking through both the AMD and OpenVSA source and it looks as if the 
>> lxvg module is supposed to handle VGA SMIs but I cannot find where this 
>> is actually done.
> None of it - the VGA is actually a seperate component under difference
> licensing.  Thats why you don't see it in the VSA code.

This is quite an important point, as a lot of programs access the I/O 
ports and framebuffer directly.  A VGA BIOS would be able to handle the 
functions provided by INT 10 but in my experience, that would not be 

>> Incidentally, I have noticed that the AMD VSA source available from 
>> dev.laptop.org cannot be used to build an image with CS5536 support.  Is 
>> this an old version and, if so, is newer source available?
> Umm...
> http://dev.laptop.org/git?p=geode-vsa;a=blob;f=sysmgr/cs5536.c;h=422922cab808fa8ca529726c2ab43e76b4289406;hb=HEAD

Please note lines 139-143:

When I attempted to build an image, it defaulted to the CS5530.  I did 
wonder about fudging the header to use the CS5536 device ID but I also 
noticed that the size of my image came to 60,466 bytes whereas the 
standard binary image is 57,504 bytes.  This would imply a significant 
difference in either the source tree, my build environment or both.

I am using the tools supplied with version 3790.1830 of the Windows 
Driver Development Kit apart from MASM, which is version 6.14.8444.

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