linux-kernel - Re: [PATCH 06/10] PM / OPP: Add dev_pm_opp_get_sharing

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Message-ID: <20160427025922.GC22326@vireshk-i7>
Date:	Wed, 27 Apr 2016 08:29:22 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	Rafael Wysocki <rjw@...ysocki.net>,
	Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
	linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
	arnd.bergmann@...aro.org, andrew@...n.ch,
	gregory.clement@...e-electrons.com, jason@...edaemon.net,
	sebastian.hesselbarth@...il.com,
	thomas.petazzoni@...e-electrons.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/10] PM / OPP: Add dev_pm_opp_get_sharing_cpus()

On 22-04-16, 15:21, Stephen Boyd wrote:
> On 04/21, Viresh Kumar wrote:
> > diff --git a/drivers/base/power/opp/cpu.c b/drivers/base/power/opp/cpu.c
> > index 55cbf9bd8707..9c4eb90759fb 100644
> > --- a/drivers/base/power/opp/cpu.c
> > +++ b/drivers/base/power/opp/cpu.c
> > @@ -329,3 +329,48 @@ int dev_pm_opp_set_sharing_cpus(struct device *cpu_dev, cpumask_var_t cpumask)
> >  	return ret;
> >  }
> >  EXPORT_SYMBOL_GPL(dev_pm_opp_set_sharing_cpus);
> > +
> > +/**
> > + * dev_pm_opp_get_sharing_cpus() - Get cpumask of CPUs sharing OPPs with @cpu_dev
> > + * @cpu_dev:	CPU device for which we do this operation
> > + * @cpumask:	cpumask to update with information of sharing CPUs
> > + *
> > + * This updates the @cpumask with CPUs that are sharing OPPs with @cpu_dev.
> > + *
> > + * Returns -ENODEV if OPP table isn't already present.
> > + *
> > + * Locking: The internal opp_table and opp structures are RCU protected.
> > + * Hence this function internally uses RCU updater strategy with mutex locks
> > + * to keep the integrity of the internal data structures. Callers should ensure
> > + * that this function is *NOT* called under RCU protection or in contexts where
> > + * mutex cannot be locked.
> > + */
> > +int dev_pm_opp_get_sharing_cpus(struct device *cpu_dev, cpumask_var_t cpumask)
> 
> Is there a reason we use cpumask_var_t instead of struct cpumask *
> here? My understanding is that cpumask_var_t is for stack
> declarations.

Just because we have been using that *consistently* everywhere in cpufreq and
OPP core.

I am fine with cpumask * as well, but we should be consistent.

So, I will keep it cpumask_var_t for this patch, and lets see if we want to
change all occurrences of the same in cpufreq and OPP core.

Sounds reasonable ?

-- 
viresh