linux-kernel - Re: [PATCH] iio: dac: max5821: convert device register to device managed function

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Date:   Mon, 19 Jul 2021 12:24:50 -0300
From:   Théo Borém Fabris <theobf@....br>
To:     Alexandru Ardelean <ardeleanalex@...il.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        linux-iio <linux-iio@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iio: dac: max5821: convert device register to device
 managed function

Hi, Alexandru.

Em seg., 19 de jul. de 2021 às 04:33, Alexandru Ardelean
<ardeleanalex@...il.com> escreveu:
>
> On Sun, Jul 18, 2021 at 11:42 PM Théo Borém Fabris <theobf@....br> wrote:
> >
> > Add a device managed hook, via devm_add_action_or_reset() and
> > max5821_regulator_disable(), to disable voltage regulator on device
> > detach.
> > Replace iio_device_register() by devm_iio_device_register() and remove
> > the max5821_remove() function used to unregister the device and disable the
> > voltage regulator.
> > Remove i2c_set_clientdata() from the probe function, since
> > i2c_get_clientdata() is not used anymore.
>
> Looks good overall.
> A few comments inline.
>
> >
> > Signed-off-by: Théo Borém Fabris <theobf@....br>
> > ---
> >  drivers/iio/dac/max5821.c | 30 ++++++++++++++++--------------
> >  1 file changed, 16 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/iio/dac/max5821.c b/drivers/iio/dac/max5821.c
> > index bd6e75699a63..44c04ae70b32 100644
> > --- a/drivers/iio/dac/max5821.c
> > +++ b/drivers/iio/dac/max5821.c
> > @@ -294,6 +294,13 @@ static const struct iio_info max5821_info = {
> >         .write_raw = max5821_write_raw,
> >  };
> >
> > +static void max5821_regulator_disable(void *data)
> > +{
> > +       struct regulator *rdata = data;
> > +
> > +       regulator_disable(rdata);
>
> This can be simplified a bit:
>
> static void max5821_regulator_disable(void *reg)
> {
>       regulator_disable(reg);
> }
>
> I used to do explicit casting, but then I also figured that it's not necessary.
>
Ok.

> > +}
> > +
> >  static int max5821_probe(struct i2c_client *client,
> >                         const struct i2c_device_id *id)
> >  {
> > @@ -306,7 +313,6 @@ static int max5821_probe(struct i2c_client *client,
> >         if (!indio_dev)
> >                 return -ENOMEM;
> >         data = iio_priv(indio_dev);
> > -       i2c_set_clientdata(client, indio_dev);
> >         data->client = client;
> >         mutex_init(&data->lock);
> >
> > @@ -331,6 +337,14 @@ static int max5821_probe(struct i2c_client *client,
> >                 goto error_free_reg;
> >         }
> >
> > +       ret = devm_add_action_or_reset(&client->dev, max5821_regulator_disable,
> > +                                      data->vref_reg);
> > +       if (ret) {
> > +               dev_err(&client->dev,
> > +                       "Failed to add action to managed regulator: %d\n", ret);
> > +               goto error_disable_reg;
>
> return ret;
>
> devm_add_action_or_reset() should call max5821_regulator_disable() in
> case of error
>
Ok.

> > +       }
> > +
> >         ret = regulator_get_voltage(data->vref_reg);
> >         if (ret < 0) {
> >                 dev_err(&client->dev,
> > @@ -346,7 +360,7 @@ static int max5821_probe(struct i2c_client *client,
> >         indio_dev->modes = INDIO_DIRECT_MODE;
> >         indio_dev->info = &max5821_info;
> >
> > -       return iio_device_register(indio_dev);
> > +       return devm_iio_device_register(&client->dev, indio_dev);
> >
> >  error_disable_reg:
>
> This entire goto block should be removed.
> The idea of using only devm_ functions is to not have these goto statements.
>
I thought the action added via devm_add_action (and devres_add) was called only
on driver detach, thus the error_disable_reg label would be necessary
to handle the
possible error on regulator_get_voltage. Could you please clarify for
me when does
a driver detach happen?

Thanks for your reply,
Théo

> >         regulator_disable(data->vref_reg);
> > @@ -356,17 +370,6 @@ static int max5821_probe(struct i2c_client *client,
> >         return ret;
> >  }
> >
> > -static int max5821_remove(struct i2c_client *client)
> > -{
> > -       struct iio_dev *indio_dev = i2c_get_clientdata(client);
> > -       struct max5821_data *data = iio_priv(indio_dev);
> > -
> > -       iio_device_unregister(indio_dev);
> > -       regulator_disable(data->vref_reg);
> > -
> > -       return 0;
> > -}
> > -
> >  static const struct i2c_device_id max5821_id[] = {
> >         { "max5821", ID_MAX5821 },
> >         { }
> > @@ -386,7 +389,6 @@ static struct i2c_driver max5821_driver = {
> >                 .pm     = &max5821_pm_ops,
> >         },
> >         .probe          = max5821_probe,
> > -       .remove         = max5821_remove,
> >         .id_table       = max5821_id,
> >  };
> >  module_i2c_driver(max5821_driver);
> > --
> > 2.20.1
> >