Re: GRUB_GFXMODE= 60 refresh how?

[Jordan Uggla]

On Sun, May 4, 2014 at 6:51 AM, Felix Miata <address@hidden> wrote:
> On 2014-05-04 15:56 (GMT+0400) Andrey Borzenkov composed:
>
>
>> Felix Miata wrote:
>
>
>>> If neither GRUB_GFXPAYLOAD_LINUX nor GRUB_GFXMODE can provide a known
>>> *supported* video mode to suit the user, why do they even exist?
>
>
>> Please provide reference to handover protocol that allows passing
>> refresh rate information between bootloader and linux kernel.
>
>
> This isn't the dev list. It's the user list.
>
> video= does work, and AFAIK it's only a few years old, having been created
> only upon introduction of KMS (which means one who cares about "handover
> protocol" shouldn't need to go too far back in kernel mailing list archives
> to find discussion of its creation); so again, what is the point of having
> GRUB_GFXPAYLOAD_LINUX or GRUB_GFXMODE?

gfxmode controls the mode grub uses for displaying its menu.
gfxpayload controls the mode that is set before transitioning control
to the kernel. vga= in grub legacy also controlled what mode was set
before transitioning control to the kernel, and before KMS, the mode
used by non-X ttys was generally determined by the mode that the
bootloader handed off to the kernel. Before KMS, both the bootloader
and the kernel's console were limited to modes available through VBE,
or other firmware specific graphics APIs. VBE is very limited, and
often does not expose the native resolution of a screen. Now that we
have KMS, native drivers can be used for the kernel's console, and we
can get the exact resolutions and refresh rates we desire.

With non-buggy graphics drivers, the value of grub's gfxmode should
not matter once booting is completed; the kernel should be able to
take the graphics card in whatever state it happens to be in, and
switch to the desired mode (by default, the native resolution/refresh
rate of the display). Some drivers have issues transitioning out of
certain states, in which case gfxpayload=text is usually the most
reliable choice on BIOS based systems, and if you want to avoid
extraneous mode switches during boot (to avoid flickering), you want
to use gfxpayload=keep, and if possible gfxmode should be set to the
mode you want to end up with at the end of boot (though, as stated
before, you're limited to the modes available via VBE,GOP,UGA, or
whatever other interfaces the boot firmware may provide for setting up
graphics.

-- 
Jordan Uggla (Jordan_U on irc.freenode.net)