linux-kernel - Re: [PATCH v2] iio: max5487: Add support for Maxim digital potentiometers

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Message-ID: <CAGhQ9Vz7S1H8BO5YqzQFj7VFn36jF6poHK+fRUOyn05KUdgTPg@mail.gmail.com>
Date:	Sun, 10 Apr 2016 14:47:10 +0200
From:	Joachim Eastwood <manabian@...il.com>
To:	Cristina Moraru <cristina.moraru09@...il.com>
Cc:	Jonathan Cameron <jic23@...nel.org>,
	Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald-Stadler <pmeerw@...erw.net>, peda@...ntia.se,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-iio@...r.kernel.org, daniel.baluta@...el.com,
	octavian.purdila@...el.com
Subject: Re: [PATCH v2] iio: max5487: Add support for Maxim digital potentiometers

Hi Cristina,

On 9 April 2016 at 10:24, Cristina Moraru <cristina.moraru09@...il.com> wrote:
> Add implementation for Maxim MAX5487, MAX5488, MAX5489
> digital potentiometers.
>
> Datasheet:
> http://datasheets.maximintegrated.com/en/ds/MAX5487-MAX5489.pdf
>
> Signed-off-by: Cristina Moraru <cristina.moraru09@...il.com>
> CC: Daniel Baluta <daniel.baluta@...el.com>
> ---
...
> +static int max5487_read_raw(struct iio_dev *indio_dev,
> +                           struct iio_chan_spec const *chan,
> +                           int *val, int *val2, long mask)
> +{
> +       struct max5487_data *data = iio_priv(indio_dev);
> +
> +       if (mask != IIO_CHAN_INFO_SCALE)
> +               return -EINVAL;
> +
> +       *val = 1000 * data->kohms;
> +       *val2 = MAX5487_MAX_POS;

Newline before return.

> +       return IIO_VAL_FRACTIONAL;
> +}
> +
> +static int max5487_write_raw(struct iio_dev *indio_dev,
> +                            struct iio_chan_spec const *chan,
> +                            int val, int val2, long mask)
> +{
> +       struct max5487_data *data = iio_priv(indio_dev);
> +
> +       switch (mask) {
> +       case IIO_CHAN_INFO_RAW:
> +               if (val < 0 || val > MAX5487_MAX_POS)
> +                       return -EINVAL;
> +               return regmap_write(data->regmap, chan->address, val);
> +       default:
> +               return -EINVAL;
> +       }
> +       return -EINVAL;

To be consistent with your max5487_read_raw() function you could do a:
       if (mask != IIO_CHAN_INFO_RAW)
               return -EINVAL;


> +static const struct iio_info max5487_info = {
> +       .read_raw = &max5487_read_raw,
> +       .write_raw = &max5487_write_raw,

Address operator should be unnecessary on functions.


> +       data->regmap = devm_regmap_init_spi(spi, &max5487_regmap_config);
> +       if (IS_ERR(data->regmap))
> +               return PTR_ERR(data->regmap);

Nothing wrong with using regmap here, but since you are only using
simple regmap_write()'s you might as well have used spi_write()
directly. I am not telling you to switch, but I don't see the point of
using regmap here.

Which reminds me; for regmap you need to select REGMAP_SPI in your
Kconfig entry.


regards,
Joachim Eastwood