More advanced power savings (rev. the DPMS extension).

Egbert Eich eich at
Tue Aug 8 01:33:21 PDT 2006

Back from vacation...

Alex Deucher writes:
 > > A lot of this is driver specific and should be left under the control
 > > of the driver. The driver should apply best practices (which may be
 > > overridden by explicite config options - some of which may be dynamic
 > > as it may be desireable to alter the driver policy at runtime other
 > > can even be static as they deal more with the ideosyncrasies of a
 > > specifc system than with user preferences).
 > > Exposing too much of the chip to a client app requires
 > > chipset specific clients to deal with power management.
 > > This begs the question why not dealing with setting the power
 > > states in the driver in the first place - and possibly just
 > > expose controls for policy).
 > I think it make sense to make power management driver specific.  There
 > may be some common features, but if we are careful and keep the
 > attributes similar, there shouldn't be a problem (works well for
 > things like brightness and contrast in Xv).  user apps could then
 > query teh server the for available options and create there own
 > inferface (check box, slider, etc.) for the option type (int, float,
 > bool).  you could even provide a "pretty" name (and even description)
 > to expose to userspace for the option.

Yes, certain features can be made driver dependent. By keeping
a registry for well known/understood features we can gather
things that are common to a set of drivers under a single interface
(panel brightness would be a good target). 
Such an interface could work somehwhat like the attribute system
for Xv (I would like to extend it so that we can have more data types,
read only attributes, an explanatory string (for  fallback interfaces)
and a device property path).

On the other hand I do not want to overburdeon people with too
many power management details. The driver should have enough
intelligence to map power saving features to states itself.
I expect we will find out soon if we need more states.


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