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    SubjectRe: Hibernation considerations
    Date
    On Tuesday, 17 July 2007 22:37, david@lang.hm wrote:
    > On Tue, 17 Jul 2007, Jeremy Maitin-Shepard wrote:
    >
    > > "Rafael J. Wysocki" <rjw@sisk.pl> writes:
    > >
    > > [snip]
    > >
    > >>> Rafael, for those of us who aren't thoroughly familiar with all the ins
    > >>> and outs of the ACPI spec, could you please summarize a list of the
    > >>> ACPI calls needed in the second and third cases above? Indicate which
    > >>> ones need to be done from within the original kernel and which should
    > >>> be done from within a kexec'd hibernation kernel.
    > >
    > >> Sure.
    > >
    > >> In the third case (ie. transition to S4) we are supposed to do the following:
    > >
    > >> (1) Upon entering the sleep state, which IMO can be done _after_ the image
    > >> has been saved:
    > >
    > > I assume you mean "in order to enter the sleep state", rather than "upon
    > > entering the sleep state". I still don't understand what you mean by
    > > "which IMO can be done _after_ the image has been saved"; as far as I
    > > understand, the last step of this process, "make the platform enter S4",
    > > is almost like a shutdown as far as the kernel is concerned (except for
    > > the tiny detail of having to call those special ACPI methods on resume);
    > > consequently, it would seem that nothing can be done after that step.
    > >
    > >> * figure out which devices can wake up
    > >> * put devices into low power states (wake-up devices are placed in the Dx
    > >> states compatible with the wake capability, the others are powered off)
    >
    > this can't be done by the image-saving kernel if that kernel doesn't know
    > about the device.

    Good observation. :-)

    Greetings,
    Rafael


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