On Fri, 29 Jan 2010, Rafael J. Wysocki wrote:
> On Friday 29 January 2010, Alan Stern wrote:
> > On Thu, 28 Jan 2010, Rafael J. Wysocki wrote:
> >
> > > > > - * If @check_resume is set and there's a resume request pending when
> > > > > - * __pm_runtime_disable() is called and power.disable_depth is zero, the
> > > > > - * function will wake up the device before disabling its run-time PM.
> > > > > */
> > > > > -void __pm_runtime_disable(struct device *dev, bool check_resume)
> > > > > +void pm_runtime_disable(struct device *dev)
> > > > > {
> > > >
> > > > Why did you decide to remove the check_resume argument? That decision
> > > > should be explained in the patch description.
> > >
> > > Well, I thought the "which is not necessary any more" would be a sufficient
> > > explanation ...
> >
> > But why is it not necessary now,
>
> Well, all of the existing callers use only one value of it, which is 'false'
> (perhaps I should write that in the changelog).
I don't understand. Isn't the existing version of pm_runtime_disable()
a caller which sets check_resume to 'true'? There certainly are places
that call pm_runtime_disable().
> > given that apparently it was necessary before? What has changed to make
> > it unnecessary?
>
> It was used in the system suspend code path in main.c (in dpm_prepare()) IIRC,
> but it was replaced by the current code.
>
> I don't really think it's useful to try to recall why it was used at one point.
> It's not used now and I don't have a usage case for it. If no one else knows
> it will be necessary, removing it is the right thing to do.
A particularly important usage case for pm_runtime_disable() is when a
bus subsystem or driver does when resuming from system sleep and the
device was already runtime-suspended when the sleep began. However in
this case (and all the other cases I'm aware of) there's no need to
check whether a resume request is pending before doing the
runtime_disable.
I wasn't saying that the patch is wrong, just asking the reason for it.
Alan Stern
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