On Wed, 6 Oct 2010, Dmitry Torokhov wrote:

quoted

quoted

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.

Alan Stern