Re: Hibernation considerations

[david@lang.hm]

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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