iio: adc: stm32: Use device_for_each_child_node_scoped()

Switching to the _scoped() version removes the need for manual
calling of fwnode_handle_put() in the paths where the code
exits the loop early. In this case that's all in error paths.

Note this would have made the bug fixed in the previous path much
less likely as it allows for direct returns.

Took advantage of dev_err_probe() to futher simplify things given no
longer a need for the goto err.

Cc: Olivier Moysan <olivier.moysan@foss.st.com>
Tested-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Acked-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/20240330185305.1319844-5-jic23@kernel.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/stm32-adc.c

@@ -2187,59 +2187,52 @@ static int stm32_adc_generic_chan_init(struct iio_dev *indio_dev,
 				       struct iio_chan_spec *channels)
 {
 	const struct stm32_adc_info *adc_info = adc->cfg->adc_info;
-	struct fwnode_handle *child;
+	struct device *dev = &indio_dev->dev;
 	const char *name;
 	int val, scan_index = 0, ret;
 	bool differential;
 	u32 vin[2];
 
-	device_for_each_child_node(&indio_dev->dev, child) {
+	device_for_each_child_node_scoped(dev, child) {
 		ret = fwnode_property_read_u32(child, "reg", &val);
-		if (ret) {
-			dev_err(&indio_dev->dev, "Missing channel index %d\n", ret);
-			goto err;
-		}
+		if (ret)
+			return dev_err_probe(dev, ret,
+					     "Missing channel index\n");
 
 		ret = fwnode_property_read_string(child, "label", &name);
 		/* label is optional */
 		if (!ret) {
-			if (strlen(name) >= STM32_ADC_CH_SZ) {
-				dev_err(&indio_dev->dev, "Label %s exceeds %d characters\n",
-					name, STM32_ADC_CH_SZ);
-				ret = -EINVAL;
-				goto err;
-			}
+			if (strlen(name) >= STM32_ADC_CH_SZ)
+				return dev_err_probe(dev, -EINVAL,
+						     "Label %s exceeds %d characters\n",
+						     name, STM32_ADC_CH_SZ);
+
 			strscpy(adc->chan_name[val], name, STM32_ADC_CH_SZ);
 			ret = stm32_adc_populate_int_ch(indio_dev, name, val);
 			if (ret == -ENOENT)
 				continue;
 			else if (ret)
-				goto err;
+				return ret;
 		} else if (ret != -EINVAL) {
-			dev_err(&indio_dev->dev, "Invalid label %d\n", ret);
-			goto err;
+			return dev_err_probe(dev, ret, "Invalid label\n");
 		}
 
-		if (val >= adc_info->max_channels) {
-			dev_err(&indio_dev->dev, "Invalid channel %d\n", val);
-			ret = -EINVAL;
-			goto err;
-		}
+		if (val >= adc_info->max_channels)
+			return dev_err_probe(dev, -EINVAL,
+					     "Invalid channel %d\n", val);
 
 		differential = false;
 		ret = fwnode_property_read_u32_array(child, "diff-channels", vin, 2);
 		/* diff-channels is optional */
 		if (!ret) {
 			differential = true;
-			if (vin[0] != val || vin[1] >= adc_info->max_channels) {
-				dev_err(&indio_dev->dev, "Invalid channel in%d-in%d\n",
-					vin[0], vin[1]);
-				ret = -EINVAL;
-				goto err;
-			}
+			if (vin[0] != val || vin[1] >= adc_info->max_channels)
+				return dev_err_probe(dev, -EINVAL,
+						     "Invalid channel in%d-in%d\n",
+						     vin[0], vin[1]);
 		} else if (ret != -EINVAL) {
-			dev_err(&indio_dev->dev, "Invalid diff-channels property %d\n", ret);
-			goto err;
+			return dev_err_probe(dev, ret,
+					     "Invalid diff-channels property\n");
 		}
 
 		stm32_adc_chan_init_one(indio_dev, &channels[scan_index], val,
@@ -2248,11 +2241,9 @@ static int stm32_adc_generic_chan_init(struct iio_dev *indio_dev,
 		val = 0;
 		ret = fwnode_property_read_u32(child, "st,min-sample-time-ns", &val);
 		/* st,min-sample-time-ns is optional */
-		if (ret && ret != -EINVAL) {
-			dev_err(&indio_dev->dev, "Invalid st,min-sample-time-ns property %d\n",
-				ret);
-			goto err;
-		}
+		if (ret && ret != -EINVAL)
+			return dev_err_probe(dev, ret,
+					     "Invalid st,min-sample-time-ns property\n");
 
 		stm32_adc_smpr_init(adc, channels[scan_index].channel, val);
 		if (differential)
@@ -2262,11 +2253,6 @@ static int stm32_adc_generic_chan_init(struct iio_dev *indio_dev,
 	}
 
 	return scan_index;
-
-err:
-	fwnode_handle_put(child);
-
-	return ret;
 }
 
 static int stm32_adc_chan_fw_init(struct iio_dev *indio_dev, bool timestamping)