On 21-07-16, 16:21, Steve Muckle wrote:
> On Thu, Jul 21, 2016 at 01:30:41PM -0700, Viresh Kumar wrote:
> > Okay, but in that case shouldn't we do something like this:
> >
> > unsigned int cpufreq_driver_resolve_freq(struct cpufreq_policy *policy,
> > unsigned int target_freq)
> > {
> > target_freq = clamp_val(target_freq, policy->min, policy->max);
> > policy->cached_target_freq = target_freq;
> >
> > if (cpufreq_driver->target_index) {
> > policy->cached_resolved_idx =
> > cpufreq_frequency_table_target(policy,
> > target_freq,
> >
> > CPUFREQ_RELATION_L);
> > return
> > policy->freq_table[policy->cached_resolved_idx].frequency;
> > }
> >
> > if (cpufreq_driver->resolve_freq)
> > return cpufreq_driver->resolve_freq(policy, target_freq);
> > }
>
> Thanks for the review.
>
> My thinking (noted in the commit text) was that the caller of
> cpufreq_driver_resolve_freq() would verify that the driver supported the
> proper calls before using this API.
Okay, but the caller isn't doing that today. Right?
> This way it can be checked once,
> presumably in a governor's init routine. Checking the pointer over and
> over again in a fast path is wasteful.
But we just can not assume the callers to always check that the driver
has a ->target() and no ->resolve_freq(), and in that case not to call
this routine. We would be forced to add a WARN_ON() in that case here
to make sure we aren't trying to access a NULL ->resolve_freq.
Over that, it will be used for a very small number of drivers which
still use the ->target() callback and anyway we are going to do a
function call for them. We can add a likely() here if that helps, but
some sort of checking is surely required IMO.
And, this is a core API, which can be used for other governor's
tomorrow :)
--
viresh
