From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chanwoo Choi Subject: Re: [PATCH v4] PM / devfreq: Fix devfreq_add_device() when drivers are built as modules. Date: Wed, 04 Jul 2018 17:32:10 +0900 Message-ID: <5B3C860A.8060404@samsung.com> References: <20180703132931.14389-1-enric.balletbo@collabora.com> <5B3C1DA6.7040507@samsung.com> <7fcd3fa4-4f57-9013-b6ff-808600eeb612@collabora.com> <5B3C84CC.2030207@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8BIT Return-path: In-reply-to: <5B3C84CC.2030207@samsung.com> Sender: linux-kernel-owner@vger.kernel.org To: Enric Balletbo i Serra , linux-kernel@vger.kernel.org Cc: kernel@collabora.com, Kyungmin Park , MyungJoo Ham , linux-pm@vger.kernel.org List-Id: linux-pm@vger.kernel.org Hi Enric, Please send this patch to stable-kernel mailing list. Regards, Chanwoo Choi On 2018년 07월 04일 17:26, Chanwoo Choi wrote: > Hi Enric, > > On 2018년 07월 04일 17:16, Enric Balletbo i Serra wrote: >> Hi Chanwoo, >> >> On 04/07/18 03:06, Chanwoo Choi wrote: >>> Hi Enric, >>> >>> On 2018년 07월 03일 22:29, Enric Balletbo i Serra wrote: >>>> 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 >>>> --- >>>> >>>> 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, 47 insertions(+), 6 deletions(-) >>>> >>>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c >>>> index 0b5b3abe054e..4ea6b19879a1 100644 >>>> --- a/drivers/devfreq/devfreq.c >>>> +++ b/drivers/devfreq/devfreq.c >>>> @@ -11,6 +11,7 @@ >>>> */ >>>> >>>> #include >>>> +#include >>>> #include >>>> #include >>>> #include >>>> @@ -221,6 +222,46 @@ static struct devfreq_governor *find_devfreq_governor(const char *name) >>>> return ERR_PTR(-ENODEV); >>>> } >>>> >>>> +/** >>>> + * try_then_request_governor() - Try to find the governor and request the >>>> + * module if is not found. >>>> + * @name: name of the governor >>> >>> Usually, devfreq used 'governor_name' indicating the name of governor. >>> you better to use 'governor_name' instead of 'name' for more readability. >>> >> >> I don't mind to change if you want. But let me try to convince you first. I used >> name for two reasons: >> 1. I saw that you are using governor_name sometimes, but find_devfreq_governor >> uses name not governor_name. IMHO the function name in these two specific cases >> 'try_then_request_governor(name)' is enough readable. > > OK. skip the my comment of changing the variable name. Thanks. > >> 2. If we want to use governor_name and then do not have the line exceeding the >> 80 characters I need to split the function in two lines. For me the readability >> is better when you have all in one line. >> >> If I did not convince you, just let me now and I'll change for governor_name :) >> > > (snip) >