Re: [linux-pm] Re: [patch] hibernation: utilize ACPI hardware signature

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Wednesday, 2 of January 2008, Nigel Cunningham wrote:
> Hi.
> 
> Rafael J. Wysocki wrote:
> > On Wednesday, 2 of January 2008, Shaohua Li wrote:
> >> ACPI defines a hardware signature. BIOS calculates the signature
> >> according to hardware configure, if hardware changes, the signature will
> >> change, in this case, S4 resume should fail.
> > 
> > The idea is fine, but I'd prefer to do that in a more straightforward way.
> > Namely, we can just:
> > * write the signature into a variable in, for example,
> >   acpi_hibernation_prepare() (then, the "old" signature value will be
> >   automatically saved in the image)
> > * compare it with a the "new" value read from the BIOS in
> >   acpi_hibernation_leave() and panic if there's a mismatch
> > * add a configuration option to disable this behavior (just in case)
> > This way we can avoid modifying the entire generic interface to add the feature
> > specific to ACPI.
> > 
> > Still, if you want the boot kernel to check the signature, which will be more
> > elegant (but please note that on x86-64 the boot kernel need not support ACPI
> > at all), you can use the (recently introduced) architecture part of the image
> > header for this purpose, without modifying the generic interface.
> 
> I suppose we can always disable this when we start to support hardware
> changing over hibernate (I have ideas in this direction - memory cold
> plugging, for a start).

Well, if we support such features, we won't be following ACPI any more.

Greetings,
Rafael