linux-kernel - Re: [PATCH v5] PM / devfreq: Fix devfreq_add_device() when drivers are built as modules.

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Date:   Wed, 18 Jul 2018 11:04:36 +0200
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     cwchoi00@...il.com
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>, kernel@...labora.com,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v5] PM / devfreq: Fix devfreq_add_device() when drivers
 are built as modules.

Hi MyungJoo,

On 05/07/18 02:13, Chanwoo Choi wrote:
> Hi Enric,
> 
> 2018-07-04 17:45 GMT+09:00 Enric Balletbo i Serra
> <enric.balletbo@...labora.com>:
>> When the devfreq driver and the governor driver are built as modules,
>> the call to devfreq_add_device() or governor_store() fails because the
>> governor driver is not loaded at the time the devfreq driver loads. The
>> devfreq driver has a build dependency on the governor but also should
>> have a runtime dependency. We need to make sure that the governor driver
>> is loaded before the devfreq driver.
>>
>> This patch fixes this bug by adding a try_then_request_governor()
>> function. First tries to find the governor, and then, if it is not found,
>> it requests the module and tries again.
>>
>> Fixes: 1b5c1be2c88e (PM / devfreq: map devfreq drivers to governor using name)
>> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
>> ---
>>
>> Changes in v5:
>> - Requested by MyungJoo and Chanwoo.
>>   - Fix returning without the lock acquired after request_module.
>> - Requested by Chanwoo.
>>   - In request governor function check if governor name is NULL or not.
>>   - Remove some unrelated changes (added/removed some blank lines).
>>
>> Changes in v4:
>> - Kept "locked" devfreq_list from the return of find_devfreq_governor() to
>>   the unlock of governor_store(). Requested by MyungJoo Ham.
>>
>> Changes in v3:
>> - Remove unneded change in dev_err message.
>> - Fix err returned value in case to not find the governor.
>>
>> Changes in v2:
>> - Add a new function to request the module and call that function from
>>   devfreq_add_device and governor_store.
>>
>>  drivers/devfreq/devfreq.c | 53 ++++++++++++++++++++++++++++++++++++---
>>  1 file changed, 49 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index 0b5b3abe054e..aa92fbf9f0dd 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
> 
> (snip)
> 
> Looks good to me.
> Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>
> 

I was expecting see also this patch in the pull request you did but I didn't
see. Is because of will be merged as a fix in current cycle? or has been forgotten?

Best regards,
 Enric


> Best Regards,
> Chanwoo Choi
>