Re: [PATCH RESEND 3/4] PM / devfreq: Fix governor_store() failing when device has no current governor

[Jie Zhan <zhanjie9@hisilicon.com>]

On 3/19/2026 5:17 PM, Yaxiong Tian wrote:
> Since devfreq_remove_governor() may clear the device's current governor
> in certain situations, while governors actually exist independently
> of the device, directly returning EINVAL in this case is inaccurate.
> 
> To fix this issue, remove this check and add relevant logic for when
> df->governor is NULL.
> 
> Fixes: 483d557ee9a3 ("PM / devfreq: Clean up the devfreq instance name in sysfs attr")
> Signed-off-by: Yaxiong Tian <tianyaxiong@kylinos.cn>
> ---
>  drivers/devfreq/devfreq.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 0bf320123e3a..4a312f3c2421 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -1425,9 +1425,6 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
>  	char str_governor[DEVFREQ_NAME_LEN + 1];
>  	const struct devfreq_governor *governor, *prev_governor;
>  
> -	if (!df->governor)
> -		return -EINVAL;
> -
>  	ret = sscanf(buf, "%" __stringify(DEVFREQ_NAME_LEN) "s", str_governor);
>  	if (ret != 1)
>  		return -EINVAL;
> @@ -1438,6 +1435,18 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
>  		ret = PTR_ERR(governor);
>  		goto out;
>  	}
> +
> +	if (!df->governor) {
> +		df->governor = governor;
> +		ret = df->governor->event_handler(df, DEVFREQ_GOV_START, NULL);
> +		if (ret) {
> +			dev_warn(dev, "%s: Governor %s not started(%d)\n",
> +				__func__, df->governor->name, ret);
> +			df->governor = NULL;
> +		}
> +		goto out;
> +	}
> +
The sequence that starts the governor, and stops, and then re-starts looks
quite weird.
Can you do a NULL pointer check before the IMMUTABLE flag check and
stopping governor, rather than this?
>  	if (df->governor == governor) {
>  		ret = 0;
>  		goto out;