On Monday, 16 July 2007 14:38, Jim Crilly wrote: > On 07/16/07 02:06:27PM +0200, Rafael J. Wysocki wrote: > > On Monday, 16 July 2007 01:49, david@xxxxxxx wrote: > > > On Mon, 16 Jul 2007, Rafael J. Wysocki wrote: > > > > > > > On Monday, 16 July 2007 00:42, david@xxxxxxx wrote: > > > >> On Mon, 16 Jul 2007, Rafael J. Wysocki wrote: > > > >> > > > >>> On Sunday, 15 July 2007 22:13, david@xxxxxxx wrote: > > > >>>> On Sun, 15 Jul 2007, Rafael J. Wysocki wrote: > > > >>>> > > > >>>>> The ACPI specification requires us to invoke some global ACPI methods > > > >>>>> during the hibernation and during the restore. Moreover, the ordering of > > > >>>>> code related to these ACPI methods may not be arbitrary (eg. some of > > > >>>>> them have to be executed after devices are put into low power states etc.). > > > >>>> > > > >>>> for a pure hibernate mode, you will be powering off the box after saving > > > >>>> the suspend image. why are there any special ACPI modes involved? > > > >>> > > > >>> Because, for example, on my machine the status of power supply (present > > > >>> vs not present) is not updated correctly after the restore if ACPI callbacks > > > >>> aren't used during the hibernation. That's just experience and it's in line > > > >>> with the ACPI spec. > > > >> > > > >> so if a machine is actually powered off the /dev/suspend process won't > > > >> work? > > > > > > > > No, it sort of works as usual, but after the restore the platform is not in the > > > > correct state. > > > > > > this is not hibernate as I and many others are thinking of it. > > > > > > hibernate as we are thinking would work on basicly any hardware, including > > > things with no ACPI or power savings support. and the system could be in > > > hibernate mode for any time period. > > > > > > for that matter, after a system is put into hibernate mode the system > > > could be completely disassembled and any components replaced and the > > > system would work after a resume (assuming you still have access to the > > > suspend image) > > > > Well, this is not how ACPI defines the S4 sleep state. If the system is in > > S4, that corresponds to our hibernation, you are _not_ allowed to disassemble > > it. > > > > I've just done an experiment on my test desktop. I had enabled suspend support > > in the CMOS setup and afterwards I made Linux hibernate in the "platform" mode. > > Then, when the system was powred on, the BIOS showed me a nice "Resume from > > hibernation" screen that is not normally displayed during boot. This clearly > > means that some information has been preserved by the platform across the > > hibernate/restore cycle. We are supposed to handle that. > > > > What I believe he's getting at is that Linux hibernation shouldn't be tied > to any ACPI states. Yes, when available and working most people will want > to enter ACPI S4 but we should still have the option of doing a normal > poweroff. With the latter method it would look just like regular power off/on > cycle to the firmware. And that would definitely be useful for things like > working around buggy ACPI implementations or supporting platforms that don't > do ACPI at all. That is the difference between the platform and shutdown > options in /sys/power/disk, isn't it? Yes, but this is not my point. The point is that there are systems that _require_ the ACPI handling to work correctly after the restore and we need to that _that_ into consideration. IOW, there are poeple for whom the non-ACPI framework won't work as expected. 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
