linux-kernel - Re: [PATCH 1/6] cpufreq: Use existing stub functions instead of IS

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Date:   Sat, 22 Jun 2019 11:12:46 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        Eduardo Valentin <edubezval@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "open list:CPU FREQUENCY SCALING FRAMEWORK" 
        <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 1/6] cpufreq: Use existing stub functions instead of
 IS_ENABLED macro

On Fri, Jun 21, 2019 at 3:23 PM Daniel Lezcano
<daniel.lezcano@...aro.org> wrote:
>
> The functions stub already exist for the condition the IS_ENABLED
> is trying to avoid.
>
> Remove the IS_ENABLED macros as they are pointless.

AFAICS, the IS_ENABLED checks are an optimization to avoid generating
pointless code (including a branch) in case CONFIG_CPU_THERMAL is not
set.

Why do you think that it is not useful?

> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> ---
>  drivers/cpufreq/cpufreq.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 85ff958e01f1..7c72f7d3509c 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1378,8 +1378,7 @@ static int cpufreq_online(unsigned int cpu)
>         if (cpufreq_driver->ready)
>                 cpufreq_driver->ready(policy);
>
> -       if (IS_ENABLED(CONFIG_CPU_THERMAL) &&
> -           cpufreq_driver->flags & CPUFREQ_IS_COOLING_DEV)
> +       if (cpufreq_driver->flags & CPUFREQ_IS_COOLING_DEV)
>                 policy->cdev = of_cpufreq_cooling_register(policy);
>
>         pr_debug("initialization complete\n");
> @@ -1469,8 +1468,7 @@ static int cpufreq_offline(unsigned int cpu)
>                 goto unlock;
>         }
>
> -       if (IS_ENABLED(CONFIG_CPU_THERMAL) &&
> -           cpufreq_driver->flags & CPUFREQ_IS_COOLING_DEV) {
> +       if (cpufreq_driver->flags & CPUFREQ_IS_COOLING_DEV) {
>                 cpufreq_cooling_unregister(policy->cdev);
>                 policy->cdev = NULL;
>         }
> --
> 2.17.1
>