Re: [PATCH V2] cpufreq: Disallow ->resolve_freq() for drivers providing ->target_index()
From: Viresh Kumar
Date: Fri Jul 22 2016 - 11:13:43 EST
On 21-07-16, 17:34, Steve Muckle wrote:
> On Fri, Jul 22, 2016 at 02:18:54AM +0200, Rafael J. Wysocki wrote:
> > > My thinking was that one of these two would be preferable:
> > >
> > > - Forcing ->target() drivers to install a ->resolve_freq callback,
> > > enforcing this at cpufreq driver init time.
> > That would have been possible, but your series didn't do that.
> > > My understanding is
> > > ->target() drivers are deprecated anyway
> > No, they aren't.
> Ok. I didn't follow Documentation/cpu-freq/cpu-drivers.txt section 1.5
> then - it suggests something about target() is deprecated, perhaps it's
> out of date.
They are kind of deprecated for the new uesrs, but we still have
handful of users of it.
> Sorry, that should've been "check that either ->target_index() or
> ->resolve_freq() is implemented."
> Implementing resolve_freq for the target() drivers and requiring it at
> driver init time is probably the better way to go though. Perhaps I can
> work on this at some point.
As I said earlier as well in one of the emails, if you are worried
about the extra 'if' check in the hot path, then wouldn't this fix it
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 3dd4884c6f9e..91d8ec4c8eb7 100644
@@ -517,7 +517,7 @@ unsigned int cpufreq_driver_resolve_freq(struct cpufreq_policy *policy,
- if (cpufreq_driver->resolve_freq)
+ if (likely(cpufreq_driver->resolve_freq))
return cpufreq_driver->resolve_freq(policy, target_freq);