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

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Message-ID: <b817a599-6564-b3d0-9c91-59c3fd5b5eb1@linaro.org>
Date:   Mon, 24 Jun 2019 11:22:19 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.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 22/06/2019 11:12, Rafael J. Wysocki wrote:
> 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?

I agree but I'm not a big fan of IS_ENABLED macros in the code when it
is possible to avoid them.

What about adding a stub for that like:

#ifdef CPU_THERMAL
static inline int cpufreq_is_cooling_dev(struct cpufreq_driver *drv)
{
	return drv->flags & CPUFREQ_IS_COOLING_DEV;
}
#else
static inline int cpufreq_is_cooling_dev(struct cpufreq_driver *drv)
{
	return 0;
}
#endif

?

>> 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
>>


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