[ubuntu-x] Hybrid graphics detection

Bryce Harrington bryce at canonical.com
Thu Nov 3 13:52:49 UTC 2011

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?


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