Re: who sets boot_params[].screen_info.orig_video_isVGA?

["Antonino A. Daplas" <adaplas@gmail.com>]

gl@dsa-ac.de wrote:
> Thanks for the reply, Matthew.
> 
> On Mon, 5 Sep 2005, Matthew Garrett wrote:
> 
>> gl@dsa-ac.de <gl@dsa-ac.de> wrote:
>>> I am trying to get intelfb running on a system with a 855GM onboard
>>> chip,
>>> and the driver exits at intelfbdrv.c::intelfb_pci_register() (2.6.13,
>>> line
>>> 814:
>>>
>>>      if (FIXED_MODE(dinfo) && ORIG_VIDEO_ISVGA != VIDEO_TYPE_VLFB) {
>>>          ERR_MSG("Video mode must be programmed at boot time.\n");
>>>          cleanup(dinfo);
>>>          return -ENODEV;
>>>      }
>>
>> This ought to be done by the bootloader if you pass a vga=foo argument.
>> The framebuffer driver doesn't know how to switch resolutions (primarily
>> because Intel won't tell anyone how to do it, so the only method is a
>> real-mode BIOS call to the VESA BIOS)
> 
> Do I get it right, that, say, if I tell grub to load a kernel and
> specify "vga=xxx" on the kernel command line, grub will interpret it,
> issue some VESA BIOS calls and fill in the screen_info struct? If so,
> the card often supports several modes (VGA, SVGA, VESA, different
> resolutions, colour depths, etc.), right? So, which one will be chosen?
> Does it depend on the specific value I give to "vga="? How do I force
> VIDEO_TYPE_VLFB (VESA VGA in graphic mode) mopde then?
> 
> BTW, I didn't find any code in grub that sets up screen_info, or it's
> very well hidden:-)

One good method is to use the "vesa" driver of Xorg/Xfree86.  Check
/var/log/X*.log and it should have a nice list of vesa mode id's that
are supported.

Then add 0x200 to any of them and use it in your vga= parameter.

Tony