Bug#565160: Linux console garbled after experimental grub-pc boot

[Robert Millan]

On Wed, Jan 20, 2010 at 05:09:13AM -0600, Jonathan Nieder wrote:
> 
> This is odd, since the only places I can see that set
> orig_video_isVGA are
> 
>  - vesa_store_mode_params_graphics() in arch/x86/boot/video-vesa.c
> and
>  - vga_probe() in arch/x86/boot/video-vga.c
> 
> The latter sets it to 1, not 0x23, so the former looks to be at
> fault.  The former is only called by vesa_set_mode() in the
> same file, and only if is_graphic is 1; and is_graphic only can
> be 1 if CONFIG_FB_BOOT_VESA_SUPPORT; and adding a #error line
> shows that for me, CONFIG_FB_BOOT_VESA_SUPPORT is not defined
> ('make arch/x86/boot/video-vesa.lst' confirms).

You're looking at legacy code.  When using modern 32-bit boot protocol,
this variable is passed by bootloader.  GRUB does this in order to enable
seamless transition (to avoid flicker, as you realized).

But it seems we need to do a better job at ensuring Linux was built with
the necessary options, otherwise it can get confused.

-- 
Robert Millan

  "Be the change you want to see in the world" -- Gandhi