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

[Yaxiong Tian]

在 2026/3/31 16:53, Jie Zhan 写道:
> On 3/31/2026 4:02 PM, Yaxiong Tian wrote:
> > 在 2026/3/31 15:16, Jie Zhan 写道:
> > > 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@xxxxxxxxxx>
> > > > ---
> > > >    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?
> > This patch only addresses the issue raised in the commit message. As for the original
> >
> > start, stop, and then restart sequence, I haven't found any problems with it so far.
> You just added the first 'start' here.
> Please see the other process in governor_store().
Could you explain what you mean?
Wouldn't it be correct to directly operate on the devices without a 
governor first and then exit?
> > > >        if (df->governor == governor) {
> > > >            ret = 0;
> > > >            goto out;