Re: [PATCH 4/7] iio: adc: stm32-adc: add support of generic channels binding

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 8 Sep 2021 17:54:49 +0200
Olivier Moysan <olivier.moysan@foss.st.com> wrote:

> Add support of generic IIO channel binding:
> ./devicetree/bindings/iio/adc/adc.yaml
> Keep support of st,adc-channels and st,adc-diff-channels
> for backward compatibility.
> 
> Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>

Hi Olivier,

A few minor things inline.

Thanks,

Jonathan

> ---
>  drivers/iio/adc/stm32-adc.c | 99 +++++++++++++++++++++++++++++++++----
>  1 file changed, 90 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
> index 2f137d14f141..ae4a314854f7 100644
> --- a/drivers/iio/adc/stm32-adc.c
> +++ b/drivers/iio/adc/stm32-adc.c
> @@ -35,7 +35,7 @@
>  #define STM32H7_BOOST_CLKRATE		20000000UL
>  
>  #define STM32_ADC_CH_MAX		20	/* max number of channels */
> -#define STM32_ADC_CH_SZ			10	/* max channel name size */
> +#define STM32_ADC_CH_SZ			16	/* max channel name size */
>  #define STM32_ADC_MAX_SQ		16	/* SQ1..SQ16 */
>  #define STM32_ADC_MAX_SMP		7	/* SMPx range is [0..7] */
>  #define STM32_ADC_TIMEOUT_US		100000
> @@ -1732,6 +1732,11 @@ static int stm32_adc_get_legacy_chan_count(struct iio_dev *indio_dev, struct stm
>  		num_channels += ret;
>  	}
>  
> +	if (!num_channels) {
> +		dev_err(indio_dev->dev.parent, "No channel found\n");
> +		return -ENODATA;

I'd return 0 and handle this at the caller.   Both because it makes this
patch more readable and because a count of 0 isn't an error of the function
reading how many they are, but rather at a higher level.

> +	}
> +
>  	return num_channels;
>  }
>  
> @@ -1792,6 +1797,73 @@ static int stm32_adc_legacy_chan_init(struct iio_dev *indio_dev,
>  	return scan_index;
>  }
>  
> +static int stm32_adc_generic_chan_init(struct iio_dev *indio_dev,
> +				       struct stm32_adc *adc,
> +				       struct iio_chan_spec *channels)
> +{
> +	struct device_node *node = indio_dev->dev.of_node;
> +	const struct stm32_adc_info *adc_info = adc->cfg->adc_info;
> +	struct device_node *child;
> +	const char *name;
> +	int val, scan_index = 0, ret;
> +	bool differential;
> +	u32 vin[2];
> +
> +	for_each_available_child_of_node(node, child) {
> +		ret = of_property_read_u32(child, "reg", &val);
> +		if (ret) {
> +			dev_err(&indio_dev->dev, "Missing channel index %d\n", ret);
> +			goto err;
> +		}
> +
> +		ret = of_property_read_string(child, "label", &name);
> +		/* label is optional */
> +		if (!ret) {
> +			if (strlen(name) >= STM32_ADC_CH_SZ) {
> +				dev_err(&indio_dev->dev, "Label %s exceeds %d characters\n",
> +					name, STM32_ADC_CH_SZ);
> +				return -EINVAL;
> +			}
> +			strncpy(adc->chan_name[val], name, STM32_ADC_CH_SZ);
> +		} else if (ret != -EINVAL) {
> +			dev_err(&indio_dev->dev, "Invalid label %d\n", ret);
> +			goto err;
> +		}
> +
> +		if (val >= adc_info->max_channels) {
> +			dev_err(&indio_dev->dev, "Invalid channel %d\n", val);
> +			ret = -EINVAL;
> +			goto err;
> +		}
> +
> +		differential = false;
> +		ret = of_property_read_u32_array(child, "diff-channels", vin, 2);
> +		/* diff-channels is optional */
> +		if (!ret) {
> +			differential = true;
> +			if (vin[0] != val || vin[1] >= adc_info->max_channels) {
> +				dev_err(&indio_dev->dev, "Invalid channel in%d-in%d\n",
> +					vin[0], vin[1]);
> +				goto err;
> +			}
> +		} else if (ret != -EINVAL) {
> +			dev_err(&indio_dev->dev, "Invalid diff-channels property %d\n", ret);
> +			goto err;
> +		}
> +
> +		stm32_adc_chan_init_one(indio_dev, &channels[scan_index], val,
> +					vin[1], scan_index, differential);
> +		scan_index++;
> +	}
> +
> +	return scan_index;
> +
> +err:
> +	of_node_put(child);
> +
> +	return ret;
> +}
> +
>  static int stm32_adc_chan_of_init(struct iio_dev *indio_dev, bool timestamping)
>  {
>  	struct device_node *node = indio_dev->dev.of_node;
> @@ -1800,15 +1872,21 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev, bool timestamping)
>  	struct iio_chan_spec *channels;
>  	int scan_index = 0, num_channels = 0, ret, i;
>  	u32 smp = 0;
> +	bool legacy = false;
>  
> -	ret = stm32_adc_get_legacy_chan_count(indio_dev, adc);
> -	if (ret < 0)
> -		return ret;
> -	num_channels = ret;
> -
> +	num_channels = of_get_available_child_count(node);
> +	/*
> +	 * If no channels have been found, fallback to channels legacy properties.
> +	 * Legacy channel properties will be ignored, if some channels are

drop the ,

Legacy channel properties will be ignored if some channels...


> +	 * already defined using the standard binding.
> +	 */
>  	if (!num_channels) {
> -		dev_err(&indio_dev->dev, "No channels configured\n");
> -		return -ENODATA;
> +		ret = stm32_adc_get_legacy_chan_count(indio_dev, adc);
> +		if (ret < 0)
> +			return ret;
> +
> +		legacy = true;

Trivial but I would set legacy at top of this if block so it is nearer the comment.

> +		num_channels = ret;
>  	}
>  
>  	if (num_channels > adc_info->max_channels) {
> @@ -1832,7 +1910,10 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev, bool timestamping)
>  	if (!channels)
>  		return -ENOMEM;
>  
> -	ret = stm32_adc_legacy_chan_init(indio_dev, adc, channels);
> +	if (legacy)
> +		ret = stm32_adc_legacy_chan_init(indio_dev, adc, channels);
> +	else
> +		ret = stm32_adc_generic_chan_init(indio_dev, adc, channels);
>  	if (ret < 0)
>  		return ret;
>  	scan_index = ret;