[Intel-gfx] [PATCH] PM / runtime: Add new helper for conditional usage count incrementation

[Rafael J. Wysocki]

On Tuesday, December 15, 2015 10:06:33 AM Alan Stern wrote:
> On Mon, 14 Dec 2015, Rafael J. Wysocki wrote:
> 
> > From: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
> > 
> > Introduce a new runtime PM function, pm_runtime_get_if_in_use(),
> > that will increment the device's runtime PM usage counter and
> > return 'true' if its status is RPM_ACTIVE and its usage counter
> > is greater than 0 at the same time ('false' will be returned
> > otherwise).
> > 
> > This is useful for things that should only be done if the device
> > is active (from the runtime PM perspective) and used by somebody
> > (as indicated by the usage counter) already and they are not worth
> > bothering otherwise.
> 
> 
> > --- linux-pm.orig/drivers/base/power/runtime.c
> > +++ linux-pm/drivers/base/power/runtime.c
> > @@ -966,6 +966,27 @@ int __pm_runtime_resume(struct device *d
> >  EXPORT_SYMBOL_GPL(__pm_runtime_resume);
> >  
> >  /**
> > + * pm_runtime_get_if_in_use - Conditionally bump up the device's usage counter.
> > + * @dev: Device to handle.
> > + *
> > + * Increment the device's runtime PM usage counter and return 'true' if its
> > + * runtime PM status is RPM_ACTIVE and its usage counter is already different
> > + * from zero at the same time.  Otherwise, return 'false'.
> 
> The phrasing of this comment is slightly ambiguous (it's not clear 
> whether the "if" clause applies to both the increment and the return 
> or just the return).  IMO it would be somewhat better to write:
> 
> 	If the runtime PM status is RPM_ACTIVE and the runtime PM usage
> 	counter is nonzero, increment the counter and return 'true'.
> 	Otherwise return false without changing the counter.

Yes, that sounds better, thanks!

I'll resend the patch with that modification.

Thanks,
Rafael