On Saturday, 5 May 2007 23:42, Alan Stern wrote: > On Sat, 5 May 2007, Rafael J. Wysocki wrote: > > > > > Yes, but that can be done in two different ways: > > > > > > > > 1) "We have restored the hibernation image, but the BIOS state corresponds to > > > > a fresh reboot, so please initialize everything from scratch." > > > > > > > > 2) "We have restored the hibernation image and the ACPI S4 was used for > > > > powering off (hint: you may try not to initialize everything from scratch)." > > > > > > > > Of course, in the case 2) we are responsible for ensuring that the contents of > > > > the hibernation image are consistent with the information preserved by the > > > > BIOS. > > > > > > Keep in mind also that before you can do either 1) or 2), the boot kernel > > > has already communicated with the BIOS, possibly changing some of the ACPI > > > state. > > > > That's correct, but it follows from the ACPI spec that there is a way for the > > boot kernel to distinguish 'normal' boot from 'S4 resume' boot. If this > > mechanism is used and the boot kernel states that it's doing a 'S4 resume', > > it will be able to leave ACPI alone and restore the hibernation image. > > Okay, good. That means part of the resume-from-hibernation handling must > be included in the standard startup code of the ACPI driver, because it > runs in the boot kernel rather than the restored kernel. Does it work > that way now? You'd think it must... Well, I'm not sure, but I don't think so. It looks like the ACPI code that we use in the hibernation/suspend code paths is not in a good shape in general. IOW, we may want to implement that in the future, but I'd rather like to get 1) working reliably for everyone first. > The restored kernel could do either 1) or 2), I don't see that it matters > much which. 1) might be safer, because it's possible that external power > was turned off at some point during the hibernation (and no battery power > was available). I think that the 'ACPI S4' handling adds quite a lot of complexity to the picture and should be added on top of a working infrastructure, as an extension. Currently, we don't handle the hibernation in accordance with the ACPI spec anyway. Greetings, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
