F11: x86_64: Different boot styles

James Wilkinson fedora at aprilcottage.co.uk
Tue Sep 15 19:38:33 UTC 2009

Tom Horsley wrote:
> Speaking of mode setting, is there any legitimate reason for
> dragging stuff like that into the kernel? Isn't that normally
> the sort of thing that gets moved out of the kernel?

Not really, hardware drivers normally belong in the kernel (at least
low-level stuff).

    There are a lot of reasons for doing this, starting with simple
    robustness. It would also enable better suspend and resume support,
    and better handling of panics: if the system goes into an oops, an
    in-kernel mode-setting routine can switch back to a text mode,
    allowing the oops text to actually be read.

(During an oops, userspace isn’t running, so the kernel can’t rely on X
to do mode switching. During suspend and resume, doing modesetting in
the kernel rather than in userspace means the kernel has a better idea
of the state the graphics are in, and can display diagnostics while
userspace isn’t running).

    There is a lot of interest in supporting multiple, simultaneous X
    sessions on the same screen without using Linux virtual terminals;
    the goal here is to enable fast switching between user accounts. And
    there is interest in H.264 acceleration, facilitating the display of
    important things like HDTV. It seems that even contemporary CPUs can
    have trouble keeping up with HDTV streams. 
    – http://lwn.net/Articles/218380/

Hope this helps,


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