Re: [linux-pm] [RFC] input: syfs switches for SKE keypad

Dmitry Torokhov
2010-10-06T18:26:47Z

On Wed, Oct 06, 2010 at 02:19:03PM -0400, Alan Stern wrote:
> On Wed, 6 Oct 2010, Dmitry Torokhov wrote:
>
> > > > I think last time Rafael mentioned that runtime PM did not allow for
> > > > forcing power state from userspace but I wonder if it would be possible
> > > > for userspace to signal and "accelerate" the idle state for a device and
> > > > then standard runtime PM framework would kick in...
> > >
> > > Yes; drivers can implement their runtime power policy any way they
> > > want. For example, a driver could create a sysfs attribute file which
> > > userspace could use to ask for changes in the power state.
> > >
> > > The real question is whether the driver is platform-specific. If it is
> > > then fine, it can do whatever it wants. If it isn't then it should
> > > try to avoid doing things that are tied to a specific platform.
> > >
> >
> > No, I really think it is wrong. This what leads us to the situation we
> > are in at the moment. Every device [re]implements its own little knobs
> > to do power management. Accelerometers export their (often tailored to a
> > specific platform) attributes in sysfs in nonstandard way. And so on,
> > and so forth.
> >
> > Here I'd like to see these (PM) hooks done on device core level, i.e.
> > the knobs should be unified and live in /sys/devices/.../deviceX/power/
>
> I haven't followed this thread in detail. What sort of knobs are you
> talking about? That is, what needs to be done? Maybe the PM core
> already provides these features.
>

Mobile folks wish to power down some devices (most often input -
touchscreen, keypad) under certain circumstances to save power.
So far they were doing that by adding "disable" hook to individual
drivers and while I did allow that in for some devices I feel that we
need more standardised solution, preferably one that could re-use
existing PM hooks in drivers.

--
Dmitry