linux-kernel - Re: [PATCH v2 1/5] PM / OPP: Introduce a power estimation helper

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Message-ID: <20190131093418.umsbh4eevgod42sh@queper01-lin>
Date:   Thu, 31 Jan 2019 09:34:21 +0000
From:   Quentin Perret <quentin.perret@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Matthias Kaehlcke <mka@...omium.org>, sudeep.holla@....com,
        rjw@...ysocki.net, nm@...com, sboyd@...nel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, dietmar.eggemann@....com
Subject: Re: [PATCH v2 1/5] PM / OPP: Introduce a power estimation helper

On Thursday 31 Jan 2019 at 12:52:09 (+0530), Viresh Kumar wrote:
> On 30-01-19, 11:07, Matthias Kaehlcke wrote:
> > On Wed, Jan 30, 2019 at 05:05:02PM +0000, Quentin Perret wrote:
> > > +static int __maybe_unused _get_cpu_power(unsigned long *mW, unsigned long *kHz,
> > > +					 int cpu)
> > 
> > why __maybe_unused?
> 
> Yeah, it isn't required I think. He probably added it for the case
> where CONFIG_ENERGY_MODEL=n, but even then an inline routine is
> defined which will accept it as argument and wouldn't do anything with
> it. Had it been a macro, we would have required __maybe_unused but not
> now.

The thing is, the EM_DATA_CB() macro _is_ stubbed for
CONFIG_ENERGY_MODEL=n:

https://elixir.bootlin.com/linux/v5.0-rc4/source/include/linux/energy_model.h#L165

So, without __maybe_unused you get do get a compiler warning.

Thanks,
Quentin

> 
> -- 
> viresh