On Thursday, September 06, 2012, Rafael J. Wysocki wrote:
> On Monday, August 27, 2012, Aaron Lu wrote:
> > Currently, when we are trying to get the power state of an acpi device,
> > we will do the following:
> > If device is not power manageable, init its power state as its parent or
> > if it does not have a parent, init as D0;
> > If device is power manageable, evaluate _PSC and then refine with
> > acpi_power_get_inferred_state.
> >
> > But there exist some devices with _PSx defined, but no _PSC or _PRx.
> > It is power manageable, but the above method to get power state does
> > not cover this case and its power state will be UNKNOWN(255).
> >
> > So change the check of power manageable to whether _PSC and _PRx
> > defined.
> >
> > Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx>
>
> Applied to the linux-next branch of the linux-pm.git tree.
>
> I think it should go to -stable too and therefore it would be good to have
> it in v3.6, so I'd like to push it to Linus for -rc5, if Len has no objections.
On a second thought, perhaps the initial power state of those devices
_should_ be "unknown", hmm?
After all, we don't know what power state the device is in.
Is there any practical user-visible problem this causes to happen?
Rafael
> > ---
> > drivers/acpi/bus.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
> > index 9628652..b564e6d 100644
> > --- a/drivers/acpi/bus.c
> > +++ b/drivers/acpi/bus.c
> > @@ -207,7 +207,8 @@ static int __acpi_bus_get_power(struct acpi_device *device, int *state)
> > if (!device || !state)
> > return -EINVAL;
> >
> > - if (!device->flags.power_manageable) {
> > + if (!device->power.flags.explicit_get &&
> > + !device->power.flags.power_resources) {
> > /* TBD: Non-recursive algorithm for walking up hierarchy. */
> > *state = device->parent ?
> > device->parent->power.state : ACPI_STATE_D0;
> >
>
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