Re: [PATCH v2 18/19] staging: iio: resolver: ad2s1210: add phase_lock_range attributes

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 21 Sep 2023 09:43:59 -0500
David Lechner <dlechner@baylibre.com> wrote:

> This adds new phase_lock_range and phase_lock_range_available attributes
> to the ad2s1210 resolver driver. These attributes allow the user to set
> the phase lock range bit in the control register to modify the behavior
> of the resolver to digital converter.
> 
> Signed-off-by: David Lechner <dlechner@baylibre.com>
The guard() and scoped_guard() magic will work well in here.

Otherwise, I think as you raised in the cover letter, that the interface
needs some thought as far form obvious what a phase_lock is + nonstandard
ABI is best avoided if we can.

Jonathan

> ---
>  drivers/staging/iio/resolver/ad2s1210.c | 58 +++++++++++++++++++++++++
>  1 file changed, 58 insertions(+)
> 
> diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c
> index 71f0913b7e2e..f5b8b290e860 100644
> --- a/drivers/staging/iio/resolver/ad2s1210.c
> +++ b/drivers/staging/iio/resolver/ad2s1210.c
> @@ -259,6 +259,60 @@ static ssize_t excitation_frequency_store(struct device *dev,
>  	return ret;
>  }
>  
> +static ssize_t phase_lock_range_show(struct device *dev,
> +				     struct device_attribute *attr,
> +				     char *buf)
> +{
> +	struct ad2s1210_state *st = iio_priv(dev_to_iio_dev(dev));
> +	int ret;
> +
> +	mutex_lock(&st->lock);
> +	ret = regmap_test_bits(st->regmap, AD2S1210_REG_CONTROL,
> +			       AD2S1210_PHASE_LOCK_RANGE_44);
> +	if (ret < 0)
> +		goto error_ret;
> +
> +	ret = sprintf(buf, "%d\n", ret ? 44 : 360);
> +
> +error_ret:
> +	mutex_unlock(&st->lock);
> +	return ret;
> +}
> +
> +static ssize_t phase_lock_range_store(struct device *dev,
> +				      struct device_attribute *attr,
> +				      const char *buf, size_t len)
> +{
> +	struct ad2s1210_state *st = iio_priv(dev_to_iio_dev(dev));
> +	u16 udata;
> +	int ret;
> +
> +	ret = kstrtou16(buf, 10, &udata);
> +	if (ret < 0 || (udata != 44 && udata != 360))
> +		return -EINVAL;
> +
> +	mutex_lock(&st->lock);
> +
> +	ret = regmap_update_bits(st->regmap, AD2S1210_REG_CONTROL,
> +				 AD2S1210_PHASE_LOCK_RANGE_44,
> +				 udata == 44 ? AD2S1210_PHASE_LOCK_RANGE_44 : 0);
> +	if (ret < 0)
> +		goto error_ret;
> +
> +	ret = len;
> +
> +error_ret:
> +	mutex_unlock(&st->lock);
> +	return ret;
> +}
> +
> +static ssize_t phase_lock_range_available_show(struct device *dev,
> +					       struct device_attribute *attr,
> +					       char *buf)
> +{
> +	return sprintf(buf, "44 360\n");
> +}
> +
>  /* read the fault register since last sample */
>  static ssize_t ad2s1210_show_fault(struct device *dev,
>  				   struct device_attribute *attr, char *buf)
> @@ -506,6 +560,8 @@ static int ad2s1210_write_raw(struct iio_dev *indio_dev,
>  }
>  
>  static IIO_DEVICE_ATTR_RW(excitation_frequency, 0);
> +static IIO_DEVICE_ATTR_RW(phase_lock_range, 0);
> +static IIO_DEVICE_ATTR_RO(phase_lock_range_available, 0);
>  static IIO_DEVICE_ATTR(fault, 0644,
>  		       ad2s1210_show_fault, ad2s1210_clear_fault, 0);
>  
> @@ -552,6 +608,8 @@ static const struct iio_chan_spec ad2s1210_channels[] = {
>  
>  static struct attribute *ad2s1210_attributes[] = {
>  	&iio_dev_attr_excitation_frequency.dev_attr.attr,
> +	&iio_dev_attr_phase_lock_range.dev_attr.attr,
> +	&iio_dev_attr_phase_lock_range_available.dev_attr.attr,
>  	&iio_dev_attr_fault.dev_attr.attr,
>  	&iio_dev_attr_los_thrd.dev_attr.attr,
>  	&iio_dev_attr_dos_ovr_thrd.dev_attr.attr,