On Sun, May 4, 2014 at 6:51 AM, Felix Miata <[email protected]> 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) _______________________________________________ Help-grub mailing list [email protected] https://lists.gnu.org/mailman/listinfo/help-grub
