[SeaBIOS] cbvga

Marc Jones marcj303 at gmail.com
Tue Sep 30 20:40:26 CEST 2014

On Tue, Sep 30, 2014 at 7:06 AM, Kevin O'Connor <kevin at koconnor.net> wrote:
> On Mon, Sep 29, 2014 at 11:27:33PM -0600, Marc Jones wrote:
>> I'm trying to use the cbvga after a coreboot has initialized graphics.
>> It looks like everything is fine, but I don't get any seabios text on
>> the screen. It seems that int10 isn't working. Grub is able to display
>> fine. Does anyone know if Grub uses int10 or direct b8000 accress?
>> Scan for VGA option rom
>> Running option rom at c000:0003
>> Start SeaVGABIOS (version ?-20140929_231635-megaman)
>> enter vga_post:
>>    a=00000000  b=0000ffff  c=00000000  d=0000ffff ds=0000 es=f000 ss=0000
>>   si=00000000 di=000087b0 bp=00000000 sp=00006e62 cs=f000 ip=d413  f=0000
>> coreboot vga init
>> Found FB @ c0000000 1024x768 with 16 bpp (2048 stride)
>> set VGA mode 140
>> Attempting to allocate VGA stack via pmm call to f000:d46a
>> pmm call arg1=0
>> VGA stack allocated at ef590
>> Turning on vga text mode console
>> set VGA mode 3
>> SeaBIOS (version ?-20140929_231635-megaman)
> You don't see any output from SeaBIOS (no version banner and no boot
> menu prompt)?
> Is the framebuffer really at 0xc0000000 (as the log reports) or at
> 0xb8000 (as your question states)?  In my tests grub uses int10
> instead of 0xb8000, but if it detects a vbe adapter it will setup a
> graphical framebuffer and then write to that.  Do you see seavgabios
> debug messages showing grub probing for vbe later in the log?  Is the
> grub output you do see in graphics mode or text mode?

I don't get any output from SeaBIOS. The framebuffer is at 0xc0000000.
I asked about b8000 since that is the legacy area and I wasn't certain
how grub does things. I didn't capture any additional ouptut while
grub was loading. I assume that it is doing the vbe setup as you said.
I can do some additional debug and instrument the int10s.

Thanks for the tips.

> -Kevin


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