On Thu, 3 Dec 2009, Oliver Neukum wrote: > Am Donnerstag, 3. Dezember 2009 20:52:15 schrieb Alan Stern: > > > That's not necessarily so. If remote wakeup is disabled at a device > > between the CPU and the source device, then wakeup events are indeed > > allowed to get lost. For example, even though a USB hub may be enabled > > for remote wakeup, if its host controller isn't then a wakeup event > > won't generate an IRQ and so won't awaken the system. And in fact this > > behavior may be desired by the user. After all, who would want their > > laptop to wake up merely because a USB mouse was unplugged? > > That is no problem while the system is asleep. It is no good once the system > wakes up. Of course. That's part of the reason why we will have two separate controls for remote wakeup: one for runtime PM and one for system sleep. > > > But the core doesn't > > > know specifics. Unless you really want to overengineer this and compute > > > the reliability of each path, resuming only those whose drivers have > > > requested that remote wakeup be enabled is the best you can do. > > > > Isn't that what I agreed drivers should do? > > If the algorithm is clear and based only on remote wakeup, why > would you want to involve drivers? 1: This criterion is based only on remote wakeup, but others aren't. There were two other criteria I mentioned in an earlier email message (power-up needed to change wakeup settings, usage count > 1). 2: The core can't make the decision about whether to power-up a device. All it can do is notify drivers that the system sleep is over; the decision about what to do then is up to the drivers. > I am afraid we are having a misunderstanding. Could you elaborate? In a nutshell: The PM core _has_ to call thaw and resume methods; otherwise drivers won't know the system sleep is over. The question is what those methods should do if the device was runtime-suspended before the sleep began. Should they power-up the device (and somehow change its runtime_status)? Or should they leave it powered down? I tried to list conditions under which a driver would have to power-up the device. If none of the conditions hold then the device may remain powered down. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
