[Linux-stm32] [PATCH 3/3] iio: adc: stm32-adc: skip adc-channels setup if none is present

[Sean Nyekjaer]

If only adc differential channels are defined driver will fail with
stm32-adc: probe of 48003000.adc:adc at 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 at geanix.com>
---
 drivers/iio/adc/stm32-adc.c | 38 +++++++++++++++++++------------------
 1 file changed, 20 insertions(+), 18 deletions(-)

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index a04fcb2dc80a..6d87cfaadb5d 100644
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -2065,28 +2065,30 @@ 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;
-		}
+	if (nchans - num_diff > 0) {
+		ret = device_property_read_u32_array(dev, "st,adc-channels", chans,
+				nchans);
+		if (ret)
+			return ret;
 
-		/* 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]);
+		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;
 			}
-		}
-		stm32_adc_chan_init_one(indio_dev, &channels[scan_index],
+
+			/* 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++;
+			scan_index++;
+		}
 	}
 
 	if (adc->nsmps > 0) {
-- 
2.39.1