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

[Yaxiong Tian <tianyaxiong@kylinos.cn>]

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@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?
>> 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;