linux-kernel - Re: [PATCH 08/11] PM / devfreq: check get_dev_status in devfreq_update

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Date:   Wed, 10 Mar 2021 01:20:12 +0900
From:   Chanwoo Choi <cwchoi00@...il.com>
To:     Dong Aisheng <aisheng.dong@....com>, linux-pm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Cc:     dongas86@...il.com, kernel@...gutronix.de, shawnguo@...nel.org,
        linux-imx@....com, linux-kernel@...r.kernel.org,
        myungjoo.ham@...sung.com, kyungmin.park@...sung.com,
        cw00.choi@...sung.com, abel.vesa@....com
Subject: Re: [PATCH 08/11] PM / devfreq: check get_dev_status in
 devfreq_update_stats

On 21. 3. 9. 오후 9:58, Dong Aisheng wrote:
> Check .get_dev_status() in devfreq_update_stats in case it's abused
> when a device does not provide it.
> 
> Signed-off-by: Dong Aisheng <aisheng.dong@....com>
> ---
>   drivers/devfreq/governor.h | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
> index 31af6d072a10..67a6dbdd5d23 100644
> --- a/drivers/devfreq/governor.h
> +++ b/drivers/devfreq/governor.h
> @@ -89,6 +89,9 @@ int devfreq_update_target(struct devfreq *devfreq, unsigned long freq);
>   
>   static inline int devfreq_update_stats(struct devfreq *df)
>   {
> +	if (!df->profile->get_dev_status)
> +		return -EINVAL;
> +

I'm considering the following method instead of returning the error
when .get_dev_status is NULL.

	if (!df->profile->get_dev_status) {
		df->last_status.total_time = 0;
		df->last_status.busy_time = 0;
		df->last_status.current_frequency = 0;
		return 0;	
	}	

>   	return df->profile->get_dev_status(df->dev.parent, &df->last_status);
>   }
>   #endif /* _GOVERNOR_H */
> 


-- 
Best Regards,
Samsung Electronics
Chanwoo Choi