Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20200904152116.2157-1-brgl@bgdev.pl> <20200904152116.2157-8-brgl@bgdev.pl>
 <20200904154144.GL230586@piout.net> <CAMpxmJWwNfLvpuB_1ba037UzVX9UEz7SzDEJuft0jv3txGRJQg@mail.gmail.com>
 <20200911122837.GC230586@piout.net>
In-Reply-To: <20200911122837.GC230586@piout.net>
From:   Bartosz Golaszewski <brgl@bgdev.pl>
Date:   Fri, 11 Sep 2020 14:33:46 +0200
Message-ID: <CAMRc=MfzGgNR_vOqgDvQGCTQMiVbbiV_OKCOg61z-8B-mEuFyQ@mail.gmail.com>
Subject: Re: [PATCH 7/8] rtc: rx8010: fix indentation in probe()
To:     Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc:     Bartosz Golaszewski <bgolaszewski@baylibre.com>,
        Alessandro Zummo <a.zummo@towertech.it>,
        linux-rtc@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, Sep 11, 2020 at 2:28 PM Alexandre Belloni
<alexandre.belloni@bootlin.com> wrote:
>
> On 07/09/2020 11:34:59+0200, Bartosz Golaszewski wrote:
> > On Fri, Sep 4, 2020 at 5:41 PM Alexandre Belloni
> > <alexandre.belloni@bootlin.com> wrote:
> > >
> > > On 04/09/2020 17:21:15+0200, Bartosz Golaszewski wrote:
> > > > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> > > >
> > > > Align the arguments passed to devm_rtc_device_register() with the upper
> > > > line.
> > > >
> > > > Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> > > > ---
> > > >  drivers/rtc/rtc-rx8010.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/rtc/rtc-rx8010.c b/drivers/rtc/rtc-rx8010.c
> > > > index 181fc21cefa8..ed8ba38b4991 100644
> > > > --- a/drivers/rtc/rtc-rx8010.c
> > > > +++ b/drivers/rtc/rtc-rx8010.c
> > > > @@ -450,7 +450,7 @@ static int rx8010_probe(struct i2c_client *client,
> > > >       }
> > > >
> > > >       rx8010->rtc = devm_rtc_device_register(&client->dev, client->name,
> > > > -             &rx8010_rtc_ops, THIS_MODULE);
> > > > +                                            &rx8010_rtc_ops, THIS_MODULE);
> > > >
> > >
> > > You have bonus points if you replace that patch by switching from
> > > devm_rtc_device_register to devm_rtc_allocate_device and
> > > rtc_register_device.
> > >
> > > More bonus points if you also set range_min and range_max and then get
> > > rid of the range checking in set_time.
> > >
> >
> > Hi Alexandre!
> >
> > I've just looked at the code and wondered why there's no devm
> > counterpart for rtc_register_device(). Then I noticed that the release
> > callback for devm_rtc_allocate_device() takes care of unregistering
> > the device. This looks like serious devres abuse to me. In general the
> > idea is for the release callback to only undo whatever the devres
> > function did and this should be opaque to the concerned resources.
> >
> > In this case I believe there's no need for the 'registered' field in
> > struct rtc_device - this structure should *not* care about this - and
> > there should be devm_rtc_register_device() whose release callback
> > would take care of the unregistering. Since this function would be
> > called after devm_rtc_allocate_device(), it would be released before
> > so the ordering should be fine.
> >
>
> Note that the input subsystem is also doing it that way which is
> probably not a good reason alone to do it like that. But, IIRC, there

I'm seeing this pattern elsewhere in the kernel too and I just
recently fixed this for MDIO. I think it's just a matter of people
copy-pasting a bad implementation.

> was an actual reason this was done this way and it was the ordering of
> the rtc_nvmem_register/rtc_nvmem_unregister with rtc_device_unregister.
> I'm not sure this is still necessary though.
>

To me - each of these should have their own 'unregister' function and
appropriate devres helpers *OR* RTC-related nvmem structures could be
set up and assigned to struct rtc_device after
devm_rtc_allocate_device() and picked up by the registration function
(and also undone by rtc_unregister_device()).

I'll try to allocate some time to look into this but it's not like
it's urgent or anything - it's just a potential improvement.

Bartosz