On Thursday, 3 May 2007 21:59, Alan Stern wrote: > On Thu, 3 May 2007, Rafael J. Wysocki wrote: > > > > This suggests that the poweroff methods be completely independent of > > > hibernation_ops (or whatever you are now calling it). Perhaps there > > > should be a separate sysfs attribute controlling whether or not wakeup is > > > enabled. If it is then poweroff should go through all the ACPI (or the > > > platform's equivalent) hoops, otherwise everything should just be turned > > > off completely. Regardless of whether the poweroff is part of a > > > hibernate sequence. > > > > Well, after reviewing the code once again I see that we already do it this > > way on ACPI systems, since the 'normal' power off is done by entering the > > ACPI S5 state. Moreover, there shouldn't be any difference between > > ACPI S4 and 'power off' with respect to the wake-up devices, so you're > > absolutely right. > > > > It seems, though, that we need to do acpi_enter_sleep_state(ACPI_STATE_S4) > > to finish the hibernation in order to avoid problems like (*) and for this purpose > > we need to use hibernation_ops earlier during the hibernation. > > But why shouldn't a "normal" poweroff enter ACPI S4? And why shouldn't a > "hibernate" poweroff enter ACPI S5? The choice of which state to enter is > independent of the reason for shutting down, right? Well, not exactly. > In other words, the choice for whether or not to call > acpi_enter_sleep_state(ACPI_STATE_S4) shouldn't depend on whether or not > you're hibernating. So it shouldn't affect the usage of hibernation_ops > at all. This works the other way around, I think. :-) Granted, some boxes require us to call acpi_enter_sleep_state(ACPI_STATE_S4) as a 'power off method' so that they work correctly after the 'return' from hibernation. If we do acpi_enter_sleep_state(ACPI_STATE_S5) instead, some things might not work on them (this is an experimental observation, I don't know what exactly the reason of it is). Now, since I have such a box, I need to do the acpi_enter_sleep_state(ACPI_STATE_S4) thing (IOW, use the 'platform' power off method) and not acpi_enter_sleep_state(ACPI_STATE_S5) (the 'shutdown' power off method). *However*, acpi_enter_sleep_state(ACPI_STATE_S4) cannot be used without previous preparations, which are made with the help of hibernation_ops. IOW, all hibernation_ops, including the ->enter() method that actually calls acpi_enter_sleep_state(ACPI_STATE_S4), are just different pieces of one (complicated) 'platform' power off method. It doesn't make sense to use the (other) hibernation_ops without the ->enter() method. Greetings, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
