[Ksummit-discuss] [TECH TOPIC] PM dependencies

[Rafael J. Wysocki]

On Saturday, May 24, 2014 11:53:28 AM Mark Brown wrote:
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> On Sat, May 24, 2014 at 01:15:56AM +0200, Rafael J. Wysocki wrote:
> > On Thursday, May 22, 2014 11:14:49 AM Mark Brown wrote:
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> > > > There are more weird cases still.  For example, we have the _DEP object in
> > > > ACPI that basically says "this device depends on that one" and there may be
> > > > no other relationship between the two whatsoever.  How are we supposed to
> > > > implement this within the existing frameworks?
> 
> > > That sounds like something that should be baked into however ACPI is
> > > hooked in already?
> 
> > No, it is not.  It is a relatively new addition to ACPI and we don't support
> > it today.  That's because it hasn't been present in the ACPI tables of any
> > production systems until recently.
> 
> > However, today we have systems with it shipping and we need to add support
> > for it.
> 
> Sorry, I wasn't clear - what I meant was that it should be something
> that can be handled based on information the ACPI implementation already
> has, I had been under the impression it got notification of all the
> basic PM transitions already?

It is called to do some low-level manipulations of device PM settings during
those transitions, but that may be after the driver's suspend callback has
run (like for PCI, for example).

Rafael