On Tuesday, 17 July 2007 18:09, Jeremy Maitin-Shepard wrote: > "Rafael J. Wysocki" <rjw@xxxxxxx> writes: > > [snip] > > > I'm afraid of one thing, though. > > > If we create a framework without ACPI (well, ACPI needs to be enabled in the > > kernel anyway for other reasons, like the ability to suspend to RAM) and then > > it turns out that we have to add some ACPI hooks to it, that might be difficult > > to do cleanly. > > > Thus, it seems reasonable to think of the ACPI handling in advance. > > As far as I understand, ACPI support is only useful for hibernate to the > extent that it allows some or all of the following features: > > - possibly shows a nice looking "hibernate" LED > - possibly allows the BIOS to show something about hibernate > - possibly allows the lid or keyboard to "wake up" (turn on) the system > > Note that properly restoring device state (or even properly determining > whether on external/mains power vs. battery) on resume is not something > that should require special hibernate ACPI support, since it should be > possible to make hibernate (and in general it will be the case that > hibernate will) look exactly like a reboot to the BIOS/ACPI/devices. > The problem that you mentioned on your system regarding power source > information would seem to just be a problem with how ACPI is > reinitialized after resuming from hibernation, which is not at all > surprising since we know it (the use of driver calls for hibernate) is > currently broken in many ways. > > It seems that enabling S4 mode should just be treated as a special > shutdown mode, independent of hibernate. In practice, it may likely > only be useful in conjunction with hibernate, but there doesn't seem to > be any reason it needs to be coupled. > > It would be useful to determine whether it is necessary to initialize > ACPI specially after "resuming" from S4 mode, though, or whether they > can be initialized normally (i.e. by a normal kernel for instance, > completely unaware of hibernate). If they can be initialized normally, > then it seems that it is unnecessary to have any ACPI S4 mode support in > the resume path, and it can merely exist as a special shutdown mode. > Note that it seems a bit odd if ACPI can't be initialized normally after > resume from S4 (and still work), since the "load image" kernel > initializes everything normally before attempting to resume the > hibernated system. Unfortunately, this is more complicated (please see my recent reply to David). Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
