Re: [PATCH v2 3/4] PM / devfreq: Fix governor_store() failing when device has no current governor

[Yaxiong Tian]

在 2026/4/30 06:28, Choi Chanwoo 写道:
> 2026-04-01 PM 12:31에 Yaxiong Tian 이(가) 쓴 글:
> > 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@xxxxxxxxxx>
> > ---
> >   drivers/devfreq/devfreq.c | 17 ++++++++++++++---
> >   1 file changed, 14 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> > index 2977b07be939..975f82d7a9d1 100644
> > --- a/drivers/devfreq/devfreq.c
> > +++ b/drivers/devfreq/devfreq.c
> > @@ -1390,9 +1390,6 @@ 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;
> > @@ -1403,6 +1400,20 @@ 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;
> > +		} else {
> > +			ret = sysfs_update_group(&df->dev.kobj, &gov_attr_group);
> > +		}
> > +		goto out;
> > +	}
> > +
> >   	if (df->governor == governor) {
> >   		ret = 0;
> >   		goto out;
> Hi,
>
> I think that the following patch is able to support on your case.
> Could you please check it?
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index e5d3f9cf94dc..f08fc6966eae 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -1390,9 +1390,6 @@ 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;
> @@ -1403,6 +1400,9 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
>                  ret = PTR_ERR(governor);
>                  goto out;
>          }
> +       if (!df->governor)
> +               goto start_new_governor;
> +
>          if (df->governor == governor) {
>                  ret = 0;
>                  goto out;
> @@ -1423,6 +1423,7 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
>                  goto out;
>          }
>   
> +start_new_governor:
>          /*
>           * Start the new governor and create the specific sysfs files
>           * which depend on the new governor.
> @@ -1436,6 +1437,9 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
>   
>                  /* Restore previous governor */
>                  df->governor = prev_governor;
> +               if (!df->governor)
> +                       goto out;
> +
>             
>
> Thanks,
> Chanwoo Choi
Of course. I have tested it, and this patch is fine. So if you have 
already prepared
the patch, you can add my Reviewed-by tag:
Reviewed-by: Yaxiong Tian tianyaxiong@xxxxxxxxxx.
Or directly use my V3 version:
https://lore.kernel.org/all/20260430032035.75496-1-tianyaxiong@xxxxxxxxxx/