[PATCH v2] iio: adc: stm32-adc: fix possible division by zero in processed channel

[Andy Shevchenko]

On Wed, Sep 16, 2026 at 05:20:48PM +0200, Fabrice Gasnier wrote:
> On 9/16/26 16:39, Andy Shevchenko wrote:

[ snip ]

> > Let's look at the current code in this switch-case
> 
> Thanks for you suggestions !
> 
> Let's keep in the picture the 'normal' raw case:

Ah, an important detail!

> 	case IIO_CHAN_INFO_RAW:
> > 	case IIO_CHAN_INFO_PROCESSED:
> > 		if (!iio_device_claim_direct(indio_dev))
> > 			return -EBUSY;
> > 		if (chan->type == IIO_VOLTAGE)
> > 			ret = stm32_adc_single_conv(indio_dev, chan, val);
> > 		else
> > 			ret = -EINVAL;
> > 
> > 		if (mask == IIO_CHAN_INFO_PROCESSED)
> > 			*val = STM32_ADC_VREFINT_VOLTAGE * adc->vrefint.vrefint_cal / *val;
> > 
> > 		iio_device_release_direct(indio_dev);
> > 		return ret;
> > 
> > In the previous version you were trying to keep goto-less approach.
> > However in the current state of affairs I don't think the goto is
> > too bad (after all we need to backport this to the kernels that may
> > not have IIO_DEV_ACQUIRE_DIRECT_MODE() macro).
> > 
> > Also checking 'ret' under another condition seems unusual.
> > 
> > What about
> > 
> > 	case IIO_CHAN_INFO_PROCESSED:
> > 		if (!iio_device_claim_direct(indio_dev))
> > 			return -EBUSY;
> > 		if (chan->type == IIO_VOLTAGE)
> > 			ret = stm32_adc_single_conv(indio_dev, chan, val);
> > 		else
> > 			ret = -EINVAL;
> > 		iio_device_release_direct(indio_dev);
> > 		if (ret)
> > 			return ret;
> > 
> > 		if (*val == 0)
> > 			return -EINVAL;
> 
> So *val == 0 is normally a valid value, for 'normal' raw channels.
> 
> > 		if (mask == IIO_CHAN_INFO_PROCESSED)
> > 			*val = STM32_ADC_VREFINT_VOLTAGE * adc->vrefint.vrefint_cal / *val;
> 
> With you suggestion, moving if (*val == 0) to here should be fine ?

Yep.

> 		if (mask == IIO_CHAN_INFO_PROCESSED) {
> 			if (*val == 0)
> 				return -EINVAL;
> 			*val = STM32_ADC_VREFINT_VOLTAGE * adc->vrefint.vrefint_cal / *val;
> 		}
> 
> > 		return 0;
> > 
> > ? (Yes, we leave that line untouched, but we get the change cleaner.)

-- 
With Best Regards,
Andy Shevchenko