Re: [PATCH v2 2/2] iio: adc: stm32-adc: skip adc-channels setup if none is present

[Olivier MOYSAN <olivier.moysan@foss.st.com>]

Hi Sean,

Sorry for late answer. I was ooo. Please, find my comment below.

On 4/21/23 13:35, Sean Nyekjaer wrote:
> If only adc differential channels are defined driver will fail with
> stm32-adc: probe of 48003000.adc:adc@0 failed with error -22
> 
> Fix this by skipping the initialization if no channels are defined.
> 
> This applies only to the legacy way of initializing adc channels.
> 
> Fixes: d7705f35448a ("iio: adc: stm32-adc: convert to device properties")
> Signed-off-by: Sean Nyekjaer <sean@geanix.com>
> ---
> Changes since v1:
>   - Ignore extra channel for timestamps in PIO mode
>   - Use single ended count in channel creation (Thanks Olivier Moysan)
> 
>   drivers/iio/adc/stm32-adc.c | 40 ++++++++++++++++++-------------------
>   1 file changed, 20 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
> index 14524c1b5583..99bfe995b6f1 100644
> --- a/drivers/iio/adc/stm32-adc.c
> +++ b/drivers/iio/adc/stm32-adc.c
> @@ -2038,6 +2038,7 @@ static int stm32_adc_legacy_chan_init(struct iio_dev *indio_dev,
>   	struct stm32_adc_diff_channel diff[STM32_ADC_CH_MAX];
>   	struct device *dev = &indio_dev->dev;
>   	u32 num_diff = adc->num_diff;
> +	int num_se = nchans - num_diff;
>   	int size = num_diff * sizeof(*diff) / sizeof(u32);
>   	int scan_index = 0, ret, i, c;
>   	u32 smp = 0, smps[STM32_ADC_CH_MAX], chans[STM32_ADC_CH_MAX];
> @@ -2065,28 +2066,27 @@ static int stm32_adc_legacy_chan_init(struct iio_dev *indio_dev,
>   		}
>   	}
>   
> -	ret = device_property_read_u32_array(dev, "st,adc-channels", chans,
> -					     nchans);
> -	if (ret)
> -		return ret;
> -
> -	for (c = 0; c < nchans; c++) {
> -		if (chans[c] >= adc_info->max_channels) {
> -			dev_err(&indio_dev->dev, "Invalid channel %d\n",
> -				chans[c]);
> -			return -EINVAL;
> -		}
> -
> -		/* Channel can't be configured both as single-ended & diff */
> -		for (i = 0; i < num_diff; i++) {
> -			if (chans[c] == diff[i].vinp) {
> -				dev_err(&indio_dev->dev, "channel %d misconfigured\n",	chans[c]);
> +	ret = device_property_read_u32_array(dev, "st,adc-channels", chans, num_se);

I can see a change on device_property_read_u32_array() return check.
 From device_property_read_u32_array() doc, we should avoid calling the 
function with num_se=0 :
"It's recommended to call device_property_count_u32() instead of calling 
this function with @val equals %NULL and @nval equals 0."
Moreover, in case of error we will not return the error status here.

I propose to manage error handling as it is done for 
st,adc-diff-channels property. So, something like this:

	if (num_se > 0) {
		ret = device_property_read_u32_array(dev, "st,adc-channels", chans, 
num_se);
		if (ret) {
			dev_err(&indio_dev->dev, "Failed to get st,adc-channels %d\n", ret);
			return ret;
		}

		for (c = 0; c < num_se; c++) {

> +	if (ret == 0 && num_se > 0) {
> +		for (c = 0; c < num_se; c++) {
> +			if (chans[c] >= adc_info->max_channels) {
> +				dev_err(&indio_dev->dev, "Invalid channel %d\n",
> +					chans[c]);
>   				return -EINVAL;
>   			}
> +
> +			/* Channel can't be configured both as single-ended & diff */
> +			for (i = 0; i < num_diff; i++) {
> +				if (chans[c] == diff[i].vinp) {
> +					dev_err(&indio_dev->dev, "channel %d misconfigured\n",
> +						chans[c]);
> +					return -EINVAL;
> +				}
> +			}
> +			stm32_adc_chan_init_one(indio_dev, &channels[scan_index],
> +						chans[c], 0, scan_index, false);
> +			scan_index++;
>   		}
> -		stm32_adc_chan_init_one(indio_dev, &channels[scan_index],
> -					chans[c], 0, scan_index, false);
> -		scan_index++;
>   	}
>   
>   	if (adc->nsmps > 0) {
> @@ -2307,7 +2307,7 @@ static int stm32_adc_chan_fw_init(struct iio_dev *indio_dev, bool timestamping)
>   
>   	if (legacy)
>   		ret = stm32_adc_legacy_chan_init(indio_dev, adc, channels,
> -						 num_channels);
> +						 timestamping ? num_channels - 1 : num_channels);
>   	else
>   		ret = stm32_adc_generic_chan_init(indio_dev, adc, channels);
>   	if (ret < 0)

BRs
Olivier