Re: [PATCH] iio: adc: stm32: fix vrefint wrong calibration value handling

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 9 Jun 2022 11:58:56 +0200
Olivier Moysan <olivier.moysan@foss.st.com> wrote:

> If the vrefint calibration is zero, the vrefint channel output value
> cannot be computed. Currently, in such case, the raw conversion value
> is returned, which is not relevant.
> Do not expose the vrefint channel when the output value cannot be
> computed, instead.
> 
> Fixes: 0e346b2cfa85 ("iio: adc: stm32-adc: add vrefint calibration support")
> 
No line break here. Fixes is part of the tag block (and a pull request sent with
this gap will get rejected). Fixed up whilst applying.
> Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>

Applied to the fixes-togreg branch of iiogit.

I initially wondered if using -ENOENT for this was safe in that it couldn't
come from anywhere else.  Looks like it is given how little this function does
so fair enough.

Thanks,

Jonathan

> ---
>  drivers/iio/adc/stm32-adc.c | 27 +++++++++++++++++----------
>  1 file changed, 17 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
> index a68ecbda6480..f13c112f540f 100644
> --- a/drivers/iio/adc/stm32-adc.c
> +++ b/drivers/iio/adc/stm32-adc.c
> @@ -1365,7 +1365,7 @@ static int stm32_adc_read_raw(struct iio_dev *indio_dev,
>  		else
>  			ret = -EINVAL;
>  
> -		if (mask == IIO_CHAN_INFO_PROCESSED && adc->vrefint.vrefint_cal)
> +		if (mask == IIO_CHAN_INFO_PROCESSED)
>  			*val = STM32_ADC_VREFINT_VOLTAGE * adc->vrefint.vrefint_cal / *val;
>  
>  		iio_device_release_direct_mode(indio_dev);
> @@ -1979,10 +1979,10 @@ static int stm32_adc_populate_int_ch(struct iio_dev *indio_dev, const char *ch_n
>  
>  	for (i = 0; i < STM32_ADC_INT_CH_NB; i++) {
>  		if (!strncmp(stm32_adc_ic[i].name, ch_name, STM32_ADC_CH_SZ)) {
> -			adc->int_ch[i] = chan;
> -
> -			if (stm32_adc_ic[i].idx != STM32_ADC_INT_CH_VREFINT)
> -				continue;
> +			if (stm32_adc_ic[i].idx != STM32_ADC_INT_CH_VREFINT) {
> +				adc->int_ch[i] = chan;
> +				break;
> +			}
>  
>  			/* Get calibration data for vrefint channel */
>  			ret = nvmem_cell_read_u16(&indio_dev->dev, "vrefint", &vrefint);
> @@ -1990,10 +1990,15 @@ static int stm32_adc_populate_int_ch(struct iio_dev *indio_dev, const char *ch_n
>  				return dev_err_probe(indio_dev->dev.parent, ret,
>  						     "nvmem access error\n");
>  			}
> -			if (ret == -ENOENT)
> -				dev_dbg(&indio_dev->dev, "vrefint calibration not found\n");
> -			else
> -				adc->vrefint.vrefint_cal = vrefint;
> +			if (ret == -ENOENT) {
> +				dev_dbg(&indio_dev->dev, "vrefint calibration not found. Skip vrefint channel\n");
> +				return ret;
> +			} else if (!vrefint) {
> +				dev_dbg(&indio_dev->dev, "Null vrefint calibration value. Skip vrefint channel\n");
> +				return -ENOENT;
> +			}
> +			adc->int_ch[i] = chan;
> +			adc->vrefint.vrefint_cal = vrefint;
>  		}
>  	}
>  
> @@ -2030,7 +2035,9 @@ static int stm32_adc_generic_chan_init(struct iio_dev *indio_dev,
>  			}
>  			strncpy(adc->chan_name[val], name, STM32_ADC_CH_SZ);
>  			ret = stm32_adc_populate_int_ch(indio_dev, name, val);
> -			if (ret)
> +			if (ret == -ENOENT)
> +				continue;
> +			else if (ret)
>  				goto err;
>  		} else if (ret != -EINVAL) {
>  			dev_err(&indio_dev->dev, "Invalid label %d\n", ret);