Re: [PATCH v4 7/8] iio: adc: ad9467: convert to backend framework

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 20 Dec 2023 16:34:10 +0100
Nuno Sa <nuno.sa@analog.com> wrote:

> Convert the driver to use the new IIO backend framework. The device
> functionality is expected to be the same (meaning no added or removed
> features).
> 
> Also note this patch effectively breaks ABI and that's needed so we can
> properly support this device and add needed features making use of the
> new IIO framework.
> 
> Signed-off-by: Nuno Sa <nuno.sa@analog.com>

A few minor comments. Looks good to me.

Jonathan

> +static int ad9467_update_scan_mode(struct iio_dev *indio_dev,
> +				   const unsigned long *scan_mask)
> +{
> +	struct ad9467_state *st = iio_priv(indio_dev);
> +	unsigned int c;
> +	int ret;
> +
> +	for (c = 0; c < st->info->num_channels; c++) {
> +		if (test_bit(c, scan_mask))
> +			ret = iio_backend_chan_enable(st->back, c);
> +		else
> +			ret = iio_backend_chan_disable(st->back, c);
> +
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}

>  static int ad9467_reset(struct device *dev)
> @@ -443,25 +475,63 @@ static int ad9467_reset(struct device *dev)
>  	return 0;
>  }
>  
> +static int ad9467_iio_backend_get(struct ad9467_state *st)
> +{
> +	struct device *dev = &st->spi->dev;
> +	struct device_node *__back;
> +
> +	st->back = devm_iio_backend_get_optional(&st->spi->dev, NULL);
> +	if (IS_ERR(st->back))
> +		return PTR_ERR(st->back);

As per the comment on previous patch I'd just get it using the normal
function and handle PTR_ERR(-ENOENT) here as meaning we need to
try the old way.

> +	if (st->back)
> +		return 0;
> +	/*
> +	 * if we don't get the backend using the normal API's, use the legacy
> +	 * 'adi,adc-dev' property. So we get all nodes with that property, and
> +	 * look for the one pointing at us. Then we directly lookup that fwnode
> +	 * on the backend list of registered devices. This is done so we don't
> +	 * make io-backends mandatory which would break DT ABI.
> +	 */
> +	for_each_node_with_property(__back, "adi,adc-dev") {
> +		struct device_node *__me;
> +
> +		__me = of_parse_phandle(__back, "adi,adc-dev", 0);
> +		if (!__me)
> +			continue;
> +
> +		if (!device_match_of_node(dev, __me)) {
> +			of_node_put(__me);
> +			continue;
> +		}
> +
> +		of_node_put(__me);
> +		st->back = devm_iio_backend_get_from_fwnode_lookup(dev,
> +								   of_fwnode_handle(__back));
> +		of_node_put(__back);

If it lands first the patch
RFC PATCH 1/4] of: Add cleanup.h based autorelease via __free(device_node) markings.
will get rid of this manual handling for you for both the continue and return.
This will make a very nice example for that :)

> +		return PTR_ERR_OR_ZERO(st->back);
> +	}
> +
> +	return -ENODEV;
> +}