[SeaBIOS] cbvga

Kevin O'Connor kevin at koconnor.net
Tue Sep 30 15:06:53 CEST 2014

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?


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