Re: [RFD] How to tell ACPI drivers what the target sleep state is (was: Re: [PATCH 1/2] acpi choose sleep state help)

[Len Brown <lenb@kernel.org>]

On Wednesday 20 June 2007 07:32, Rafael J. Wysocki wrote:
> On Wednesday, 20 June 2007 08:18, Shaohua Li wrote:
> > On Tue, 2007-06-19 at 13:52 +0200, Rafael J. Wysocki wrote:
> > > On Tuesday, 19 June 2007 04:33, Shaohua Li wrote:
> > > > Based on David's patch
> > > > http://marc.info/?l=linux-acpi&m=117873972806360&w=2
> > > > I slightly changed it.
> > > > 
> > > > Add a helper routine, which gets the sleep state of a ACPI device.
> > > 
> > > Is it going to work with the recent code ordering changes?  I mean,
> > > acpi_pm_prepare() is now called after device_suspend() (and analogously for
> > > the hibernation), so the target ACPI state is not known when the drivers'
> > > .suspend() routines are being called.
> > Not. Could pm_message_t have a member indicating the suspend state?
> 
> Well, I thought about that, but I did't know what people on linux-pm would
> think about that.
> 
> Alternatively, we could introduce a pm_target() global PM operation that will
> set the target sleep state for the entire system.
> 
> I think we should discuss that on linux-pm before any decision is made.

okay, this thread include linux-pm....

I support the proposal that pm_message_t include the target state
in addition to the phase of entering that state.
The reasoning is simple, device drivers that receive a pm_message_t
will do different things depending on the target state.
The example at hand is ACPI devices that need to know how deep a D-state
to go into based on the S-state, and this in-turn depends on if they
are enabled as wakeup devices or not.

thanks,
-Len