linux-kernel - Re: [PATCH V4 3/3] cpufreq: Specify default governor on command line

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Message-ID: <20200629095038.GB1231692@google.com>
Date:   Mon, 29 Jun 2020 10:50:38 +0100
From:   Quentin Perret <qperret@...gle.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Jonathan Corbet <corbet@....net>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        kernel-team@...roid.com, tkjos@...gle.com, adharmap@...eaurora.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 3/3] cpufreq: Specify default governor on command line

On Monday 29 Jun 2020 at 10:48:25 (+0100), Quentin Perret wrote:
> On Monday 29 Jun 2020 at 15:16:27 (+0530), Viresh Kumar wrote:
> > On 29-06-20, 10:44, Quentin Perret wrote:
> > > On Monday 29 Jun 2020 at 13:55:00 (+0530), Viresh Kumar wrote:
> > > >  static int __init cpufreq_core_init(void)
> > > >  {
> > > > +	struct cpufreq_governor *gov = cpufreq_default_governor();
> > > > +
> > > >  	if (cpufreq_disabled())
> > > >  		return -ENODEV;
> > > >  
> > > >  	cpufreq_global_kobject = kobject_create_and_add("cpufreq", &cpu_subsys.dev_root->kobj);
> > > >  	BUG_ON(!cpufreq_global_kobject);
> > > >  
> > > > +	if (!strlen(default_governor))
> > > 
> > > Should we test '!strlen(default_governor) && gov' here actually?
> > > We check the return value of cpufreq_default_governor() in
> > > cpufreq_init_policy(), so I'm guessing we should do the same here to be
> > > on the safe side.
> > 
> > With the current setup (the Kconfig option being a choice which
> > selects one governor at least), it is not possible for gov to be NULL
> > here. And so I didn't worry about it :)
> 
> Right, so should we remove the check in cpufreq_init_policy() then?
> I don't mind either way as long as we are consitent :)

And actually maybe we should remove the weakly defined
cpufreq_default_governor() implementation too? That'd make sure we get a
link-time error if for some reason things change in the Kconfig options.

Thanks,
Quentin