On Sunday, August 01, 2010, Paul E. McKenney wrote: > On Sun, Aug 01, 2010 at 05:41:30PM +0200, Rafael J. Wysocki wrote: > > On Saturday, July 31, 2010, Alan Stern wrote: > > > On Sat, 31 Jul 2010, Paul E. McKenney wrote: ... > > > On Android this goes somewhat farther. IIUC, they want hardly anything > > > to run while the display is powered off. (But my understanding could > > > be wrong.) > > > > Not really. Quite a lot of things happen on these systems while the display > > is off (let alone the periodic battery monitoring on Nexus One :-)). They > > can send things over the network and do similar stuff in that state. > > > > I think the opposite is true, ie. the display is aggressively turned off > > whenever it appears not to be used, because it draws a lot of power. > > Fair enough. It appears to me that Android won't suspend if the display > is on, but I could easily be confused here. That's correct. In fact, Android uses a special mechanism called "early suspend" (or similar) to suspend the display and some other devices before the "real" suspend happens. ... > > > > o Power-naive applications must be prohibited from controlling > > > > the system power state. One acceptable approach is through > > > > use of group permissions on a special power-control device. > > > > > > You mean non-power-aware applications, not power-naive applications. > > > But then the statement is redundant; it follows directly from the > > > definition of "power-aware". > > > > Agreed. > > OK, but I still believe that an enforcement mechanism is required. The requirement is that power-oblivious applications should not participate in deciding whether or not to put the system into a sleep state which is pretty much by definition. > > > > o Statistics of the power-control actions taken by power-aware > > > > applications must be provided, and must be keyed off of program > > > > name. > > > > > > > > o Power-aware applications can make use of power-naive infrastructure. > > > > This means that a power-aware application must have some way, > > > > whether explicit or implicit, to ensure that any power-naive > > > > infrastructure is permitted to run when a power-aware application > > > > needs it to run. > > > > > > > > o When a power-aware application is preventing the system from > > > > shutting down, and is also waiting on a power-naive application, > > > > the power-aware application must set a timeout to handle > > > > the possibility that the power-naive application might halt > > > > or otherwise fail. (Such timeouts are also used to limit the > > > > number of kernel modifications required.) > > > > > > No, this is not a requirement. A power-optimized application would do > > > this, of course, by definition. But a power-aware application doesn't > > > have to. > > > > Agreed. > > Again, this requirement was explicitly called out by the Android folks. Rather, there should be a mechanism allowing PM-driving applications to do that, but they are not required to use that mechanism. Thanks, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
