On Wednesday, October 06, 2010, Dmitry Torokhov wrote: > 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. There's no interface for that at the PM core level, but I think we should add it, perhaps in analogy to the autosuspend one. Namely, we can add a flag for drivers who want to make their suspend/resume callbacks to be reachable directly from user space. Setting that flag would enable a sysfs attribute in /sys/devices/.../power/ allowing user space to invoke pm_runtime_suspend() and pm_runtime_resume() for the given device. Thanks, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
