[SeaBIOS] [PATCH 3/3] bochsvga: dynamic generation of EDID

[Gerd Hoffmann]

On 09/11/12 01:35, Hiroshi Miura wrote:
> Hi,
> 
> On 2012.09.10 15:57, Gerd Hoffmann wrote:
>> On 09/09/12 16:00, Hiroshi Miura wrote:
>>> Generate EDID according to preferred resolution
>>> from VBE_DISPI interface.
>>> +void bochs_init_preferred_resolution(u16 max_xres, u16 max_yres) {
>>> +
>>> +    if (max_xres >= 1920 && max_yres >= 1200){
>>> +        max_xres = 1920; max_yres = 1200;
>>> +    } else if (max_xres >= 1600 && max_yres >= 1200){
>>> +        max_xres = 1600; max_yres = 1200;
>>> +    } else if (max_xres >= 1280 && max_yres >= 1024){
>>> +        max_xres = 1280; max_yres = 1024;
>>> +    } else {
>>> +        max_xres = 1152; max_yres = 864;
>>> +    }
>>> +    SET_VGA(prefered_xres,max_xres);
>>> +    SET_VGA(prefered_yres,max_yres);
>>> +}
>>>      u16 max_xres = dispi_read(VBE_DISPI_INDEX_XRES);
>>> +    u16 max_yres = dispi_read(VBE_DISPI_INDEX_YRES);
>>> +    bochs_init_preferred_resolution(max_xres, max_yres);
>> So how this is supposed to work?  qemu gives you fixed max_xres and
>> max_yres values, you'll never see anything below 1600x1200 ...
>>
> 
> After implementing this in Seabios/vgabios, qemu have a
> option to provide a preferred resolution (from several alternatives) thru API.
> 
> I'd like to propose qemu to implement max_xres/max_yres generating
> from user configuration and/or real-display resolutions.
> 
> It looks chicken-egg thing, which one should implement first?
> I think vgabios is good for implement first and qemu next.

Usual way is to implement both and send patches for both seabios & qemu
to the seabios & qemu lists for review.

Once all issues are sorted the usual process is to merge the qemu
patches first, then make seabios use it.

> I know there was discussion adding API interface to provide edid data block
> from qemu. and qemu can handle such as /etc/qemu-fw/some-binary.bin
> for configuration.
> 
> This is alternative proposal for not-changing bochs API and help
> qemu to select resolution in easy way.

I don't think there is a way around changing the bochs api.  Using the
maximum resolution values instead of adding new preferred resolution
values has bad side effects.

cheers,
  Gerd