[linux-pm] [PATCH -mm 2/2] kexec jump -v11: save/restore device state

[Len Brown]

On Wed, 11 Jun 2008, Huang, Ying wrote:

> On Tue, 2008-06-10 at 14:01 -0400, Len Brown wrote:
> > 
> > On Tue, 10 Jun 2008, Huang, Ying wrote:
> > 
> > > This patch implements devices state save/restore before after kexec.
> > > 
> > > 
> > > This patch together with features in kexec_jump patch can be used for
> > > following:
> > > 
> > > - A simple hibernation implementation without ACPI support. You can
> > >   kexec a hibernating kernel, save the memory image of original system
> > >   and shutdown the system. When resuming, you restore the memory image
> > >   of original system via ordinary kexec load then jump back.
> > 
> > What part of ACPI's role in hibernation are you trying to avoid
> > 1. enabling wake devices
> > 2. removing power from the system
> > 3. something else?
> 
> ACPI S5 is used instead of S4 for this simple hibernation
> implementation. That is, before creating the hibernation image, the ACPI
> _PTS is not executed, devices are not put into low power state and wake
> devices are not enabled. After creating the hibernation image, the image
> is saved to disk and system is shutdown (go to S5). When resuming from
> hibernated image, ACPI _BFS and _WAK are not executed too.

Doesn't that resume the devices and their drivers into an unknown state?

-Len