Integrating OS power management with the X server
eich at pdx.freedesktop.org
Fri Oct 29 04:38:37 PDT 2004
Keith Packard writes:
> Around 10 o'clock on Oct 25, Nate Lawson wrote:
> > I'd like more information as to what the X server actually does with this
> > event.
> To ensure a reasonable chance of recovery, the X server switches back to
> whatever mode the video card started in. To allow the video card to be
> powered down, it also pulls all data out of the card back into memory.
> As the OS has no idea what the X server has done, there's really no
> substitute for having the X server know what's going on.
> > Is there any situation where it actually needs to veto a suspend?
> I can't think of any.
It does not veto but it delays the suspend until it is has done all
> > Does it potentially take seconds to save state?
> Yes. It has to pull all data out of the video card and potentially run
> the BIOS to get back to text mode.
Effectively it does the same as when doing a VT switch. Saving state is
actually not so bad as we don't save static register states as we have
calculated them when calculating the video mode.
> > Does it need to access other running subsystems or is it self-contained?
> Hmm. I don't think so.
Its self contained. It interfaces to a kernel device.
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