linux-kernel - Re: [PATCH v4] iio: potentiometer: add driver for Microchip MCP413X/414X/415X/416X/423X/424X/425X/426X

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Date:	Tue, 22 Mar 2016 17:10:31 +0100
From:	Joachim Eastwood <manabian@...il.com>
To:	Slawomir Stepien <sst@...zta.fm>
Cc:	Jonathan Cameron <jic23@...nel.org>,
	Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald-Stadler <pmeerw@...erw.net>,
	linux-iio@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] iio: potentiometer: add driver for Microchip MCP413X/414X/415X/416X/423X/424X/425X/426X

Hi Slawomir,

On 22 March 2016 at 16:44, Slawomir Stepien <sst@...zta.fm> wrote:
> The following functionalities are supported:
>  - write, read from volatile memory
>
> Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/22060b.pdf
>
> Signed-off-by: Slawomir Stepien <sst@...zta.fm>
> ---

> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +#include <linux/err.h>
> +
> +#include <linux/iio/iio.h>

Give that you use that you have a some OF stuff in your driver you
should also include <linux/of.h>. Same goes for <linux/mutex.h>.
I am sure this builds fine without those includes, but you should
explicitly include stuff that you use.

While you're at it you could also put the includes in alphabetic order.

> +static int mcp4131_read_raw(struct iio_dev *indio_dev,
> +                           struct iio_chan_spec const *chan,
> +                           int *val, int *val2, long mask)
> +{
> +       int err;
> +       struct mcp4131_data *data = iio_priv(indio_dev);
> +       int address = chan->channel;
> +
> +       switch (mask) {
> +       case IIO_CHAN_INFO_RAW:
> +               mutex_lock(&data->lock);
> +
> +               data->buf[0] = (address << MCP4131_WIPER_SHIFT) | MCP4131_READ;
> +               data->buf[1] = 0;
> +
> +               err = mcp4131_read(data->spi, data->buf, 2);
> +               if (err) {
> +                       mutex_unlock(&data->lock);
> +                       return err;
> +               }
> +
> +               /* Error, bad address/command combination */
> +               if (!MCP4131_CMDERR(data->buf))
> +                       return -EIO;

Missing mutex unlock here.

> +
> +               *val = MCP4131_RAW(data->buf);
> +               mutex_unlock(&data->lock);
> +
> +               return IIO_VAL_INT;
> +
> +       case IIO_CHAN_INFO_SCALE:
> +               *val = 1000 * data->cfg->kohms;
> +               *val2 = data->cfg->max_pos;
> +               return IIO_VAL_FRACTIONAL;
> +       }
> +
> +       return -EINVAL;
> +}
> +
> +static int mcp4131_write_raw(struct iio_dev *indio_dev,
> +                            struct iio_chan_spec const *chan,
> +                            int val, int val2, long mask)
> +{
> +       int err;
> +       struct mcp4131_data *data = iio_priv(indio_dev);
> +       int address = chan->channel << MCP4131_WIPER_SHIFT;
> +
> +       switch (mask) {
> +       case IIO_CHAN_INFO_RAW:
> +               if (val > data->cfg->max_pos || val < 0)
> +                       return -EINVAL;
> +               break;
> +
> +       default:
> +               return -EINVAL;
> +       }
> +
> +       mutex_lock(&data->lock);
> +
> +       data->buf[0] = address << MCP4131_WIPER_SHIFT;
> +       data->buf[0] |= MCP4131_WRITE | (val >> 8);
> +       data->buf[1] = val & 0xFF; /* 8 bits here */
> +
> +       err = spi_write(data->spi, data->buf, 2);
> +       if (err) {
> +               mutex_unlock(&data->lock);
> +               return err;
> +       }
> +       mutex_unlock(&data->lock);
> +
> +       return 0;

This last part could be written as:
  err = spi_write(data->spi, data->buf, 2);
  mutex_unlock(&data->lock);

  return err;


Other than the things I noted driver looks good to me.


regards,
Joachim Eastwood