[ubuntu-x] Hybrid graphics detection
Christopher James Halse Rogers
raof at ubuntu.com
Thu Nov 3 15:44:14 UTC 2011
On Thu, 2011-11-03 at 06:52 -0700, Bryce Harrington wrote:
> On Thu, Nov 03, 2011 at 09:29:02AM -0400, Christopher James Halse Rogers wrote:
> > > >
> > > > However, we talked about powering off the discrete card as well. My
> > > > recollection is that the X team was planning to look into that, but
> > > > there are unknowns about how and when we can do that.
> > >
> > > Chris was given a system that exhibits this problem, so we've had a
> > > chance to review it as well. We've spoken to the kernel team about the
> > > issue and I think a fix should be forthcoming down the pike. Chris can
> > > fill in mroe.
> > Simply writing "OFF" to /sys/kernel/debug/vgaswitcheroo/switch will turn
> > off the unconnected GPU on the system I've been playing with - and cuts
> > idle power consumption by > 50%.
> > For this particular system this is entirely safe - the radeon card isn't
> > hooked up to any outputs at all, so if the radeon driver is loaded then
> > the radeon card is useless. The switcheroo interface only exists when
> > radeon is loaded, so unconditionally writing "OFF" to it *on this
> > system* is the right thing to do.
> Would it make sense to make that into a udev rule?
I'm not sure that a udev rule would have the necessary context, but
either a udev rule or an upstart script would absolutely make sense.
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