On Wed, 13 Oct 2010, Mark Brown wrote: > On Wed, Oct 13, 2010 at 08:16:20AM +0200, Sundar R IYER wrote: > > > >> This isn't *really* about saving power in the individual device; it's > > >> more about stopping the device generating events that disrupt the rest > > >> of the system. Suspending the device can be one way of doing that and > > >> is useful if it can be done but is not really the immediate goal here. > > > >Runtime PM is _not_ a reliable way of preventing a device from > > >generating events. It is meant for saving energy, nothing else. > > > >If that's what this is about, then the answer is simple: Don't use > > >runtime PM to try to suppress events. > > > I think it is unfair to discriminate here about saving power and turning off > > events. I believe putting the device into power save leads to, if device permits > > preventing generating events is valid to hook up run time PM. > > This is the opposite way around to expectations - the expectation is > that runtime power management will flow from the device becoming idle > enough to turn off rather than the other way around. Absolutely. Another point worth mentioning is that a device in runtime-suspend can be resumed at any time, for a variety of reasons unconnected with anything the user does. While it is back at full power, there is nothing to stop it from generating events. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
