On Wed, 2 May 2007, Johannes Berg wrote: > On Wed, 2007-05-02 at 11:16 +0200, Pavel Machek wrote: > > > Well... the powerdown during hibernation... does not have _anything_ > > to do with snapshot/restore. It is really a very deep sleep; similar > > to soft powerdown, but not quite. Is this really a good idea? For that matter, what are the differences among the various sorts of poweroff? Which devices remain minimally powered for wakeup purposes? Anything else? In fact, shouldn't the poweroff at the end of a hibernate be exactly the same as a normal non-hibernate poweroff? Aren't drivers required to assume (during the processing after the snapshot has been restored) that power could have been lost and devices might need to be completely reinitialized? We are letting ourselves in for problems if we say that when the snapshot is restored, devices may or may not need to be reinitialized. Drivers might not be able to tell which, so they would have to reinitialize regardless, losing any advantage. Even worse, the device may _appear_ not to need reinitialization because the firmware (BIOS) has already initialized it but left it in a state that's useless for the kernel's purposes. (That's part of the reason why PRETHAW was added.) If the only remaining difference between poweroff for hibernate and normal poweroff is which wakeup devices will function, then it seems pointless. Why shouldn't the same devices work for wakeup from hibernate and wakeup from normal poweroff? Or have I misunderstood something and is this all nonsense? Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
