linux-kernel - Re: [PATCH] devfreq_cooling: pass a pointer to devfreq in the power model callbacks

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Date:	Tue, 21 Jun 2016 09:38:27 +0100
From:	Lukasz Luba <lukasz.luba@....com>
To:	Javi Merino <javi.merino@....com>, linux-pm@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <edubezval@...il.com>
Subject: Re: [PATCH] devfreq_cooling: pass a pointer to devfreq in the power
 model callbacks

Hi,

On 20/06/16 18:36, Javi Merino wrote:
> Eduardo, Rui,
>
> On Fri, Jun 03, 2016 at 10:25:31AM +0100, Javi Merino wrote:
>> When the devfreq cooling device was designed, it was an oversight not to
>> pass a pointer to the struct devfreq as the first parameters of the
>> callbacks.  The design patterns of the kernel suggest it for a good
>> reason.
>>
>> By passing a pointer to struct devfreq, the driver can register one
>> function that works with multiple devices.  With the current
>> implementation, a driver that can work with multiple devices has to
>> create multiple copies of the same function with different parameters so
>> that each devfreq_cooling_device can use the appropriate one.  By
>> passing a pointer to struct devfreq, the driver can identify which
>> device it's referring to.
>>
>> Cc: Zhang Rui <rui.zhang@...el.com>
>> Cc: Eduardo Valentin <edubezval@...il.com>
>> Reviewed-by: Punit Agrawal <punit.agrawal@....com>
>> Signed-off-by: Javi Merino <javi.merino@....com>
>> ---
>>   drivers/thermal/devfreq_cooling.c | 5 +++--
>>   include/linux/devfreq_cooling.h   | 6 ++++--
>>   2 files changed, 7 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/thermal/devfreq_cooling.c b/drivers/thermal/devfreq_cooling.c
>> index 01f0015f80dc..c549d83a0c7d 100644
>> --- a/drivers/thermal/devfreq_cooling.c
>> +++ b/drivers/thermal/devfreq_cooling.c
>> @@ -238,7 +238,7 @@ get_static_power(struct devfreq_cooling_device *dfc, unsigned long freq)
>>   		return 0;
>>   	}
>>
>> -	return dfc->power_ops->get_static_power(voltage);
>> +	return dfc->power_ops->get_static_power(df, voltage);
>>   }
>>
>>   /**
>> @@ -262,7 +262,8 @@ get_dynamic_power(struct devfreq_cooling_device *dfc, unsigned long freq,
>>   	struct devfreq_cooling_power *dfc_power = dfc->power_ops;
>>
>>   	if (dfc_power->get_dynamic_power)
>> -		return dfc_power->get_dynamic_power(freq, voltage);
>> +		return dfc_power->get_dynamic_power(dfc->devfreq, freq,
>> +						    voltage);
>>
>>   	freq_mhz = freq / 1000000;
>>   	power = (u64)dfc_power->dyn_power_coeff * freq_mhz * voltage * voltage;
>> diff --git a/include/linux/devfreq_cooling.h b/include/linux/devfreq_cooling.h
>> index 7adf6cc4b305..959714e93e5b 100644
>> --- a/include/linux/devfreq_cooling.h
>> +++ b/include/linux/devfreq_cooling.h
>> @@ -37,8 +37,10 @@
>>    *			@dyn_power_coeff * frequency * voltage^2
>>    */
>>   struct devfreq_cooling_power {
>> -	unsigned long (*get_static_power)(unsigned long voltage);
>> -	unsigned long (*get_dynamic_power)(unsigned long freq,
>> +	unsigned long (*get_static_power)(struct devfreq *devfreq,
>> +					  unsigned long voltage);
>> +	unsigned long (*get_dynamic_power)(struct devfreq *devfreq,
>> +					   unsigned long freq,
>>   					   unsigned long voltage);
>>   	unsigned long dyn_power_coeff;
>>   };
>
> If there are no objections, can you pick this for the next merge
> window?
>
> Thanks,
> Javi
>
This is very useful code, please pick it.

Reviewed-by: Lukasz Luba <lukasz.luba@....com>

Regards,
Lukasz