iio: adc: stm32-adc: skip adc-diff-channels setup if none is present

If no adc differential channels are defined driver will fail with EINVAL:
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>
Link: https://lore.kernel.org/r/20230503162029.3654093-1-sean@geanix.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 1aadb2ad2cabdf12130030d4bf8b341b0fb93c42..c105d82c3e4545983a2f313e95df60ff0bd232bd 100644 (file)
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -2006,16 +2006,15 @@ static int stm32_adc_get_legacy_chan_count(struct iio_dev *indio_dev, struct stm
         * to get the *real* number of channels.
         */
        ret = device_property_count_u32(dev, "st,adc-diff-channels");
-       if (ret < 0)
-               return ret;
-
-       ret /= (int)(sizeof(struct stm32_adc_diff_channel) / sizeof(u32));
-       if (ret > adc_info->max_channels) {
-               dev_err(&indio_dev->dev, "Bad st,adc-diff-channels?\n");
-               return -EINVAL;
-       } else if (ret > 0) {
-               adc->num_diff = ret;
-               num_channels += ret;
+       if (ret > 0) {
+               ret /= (int)(sizeof(struct stm32_adc_diff_channel) / sizeof(u32));
+               if (ret > adc_info->max_channels) {
+                       dev_err(&indio_dev->dev, "Bad st,adc-diff-channels?\n");
+                       return -EINVAL;
+               } else if (ret > 0) {
+                       adc->num_diff = ret;
+                       num_channels += ret;
+               }
        }
 
        /* Optional sample time is provided either for each, or all channels */