On Thu, 23 Jun 2011, Rafael J. Wysocki wrote: > Well, let's say this part of the documentation is slightly outdated. > > It basically refers to the model in which system suspend is a separate global > hardware or firmware operation, so the state of devices may be changed by the > BIOS or whatever takes over control in the meantime. In that case the kernel > has to ensure that the states of devices are consistent with what it thinks > about them and the simplest way to achieve that is to put the devices to > full power during resume (and back to low power if that's desirable). > > However, in the case of the systems this patchset is intended for system > suspend is achieved by putting various hardware components into low-power > states directly in a coordinated way and the system sleep state effectively > follows from the low-power states the hardware components end up in. The > system is woken up from this state by an interrupt or another mechanism under > the kernel's control. As a result, the kernel never gives control away, so > the state of devices after the resume is precisely known to it. > In consequence, it need not ensure that the state of devices is consistent with > its view, because it knows that this is the case. :-) That's true for system suspend, but it's probably not true for hibernation, even in embedded systems. Of course, many embedded systems don't use hibernation at all -- but those that do should be aware of this issue. > So the documentation should be updated to say what hardware model it is > referring to. It might be worthwhile to include a little warning about the difference between suspend and hibernate. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
