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SubjectRe: Hibernation considerations
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.

David Lang
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