power: supply: ab8500: Fix error handling when calling iio_read_channel_processed()

The ab8500_charger_get_[ac|vbus]_[current|voltage]() functions should
return an error code on error.

Up to now, an un-initialized value is returned.
This makes the error handling of the callers un-reliable.

Return the error code instead, to fix the issue.

Fixes: 97ab78ba ("power: supply: ab8500_charger: Convert to IIO ADC")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/f9f65642331c9e40aaebb888589db043db80b7eb.1719037737.git.christophe.jaillet@wanadoo.frSigned-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/ab8500_charger.c

@@ -488,8 +488,10 @@ static int ab8500_charger_get_ac_voltage(struct ab8500_charger *di)
 	/* Only measure voltage if the charger is connected */
 	if (di->ac.charger_connected) {
 		ret = iio_read_channel_processed(di->adc_main_charger_v, &vch);
-		if (ret < 0)
+		if (ret < 0) {
 			dev_err(di->dev, "%s ADC conv failed,\n", __func__);
+			return ret;
+		}
 	} else {
 		vch = 0;
 	}
@@ -540,8 +542,10 @@ static int ab8500_charger_get_vbus_voltage(struct ab8500_charger *di)
 	/* Only measure voltage if the charger is connected */
 	if (di->usb.charger_connected) {
 		ret = iio_read_channel_processed(di->adc_vbus_v, &vch);
-		if (ret < 0)
+		if (ret < 0) {
 			dev_err(di->dev, "%s ADC conv failed,\n", __func__);
+			return ret;
+		}
 	} else {
 		vch = 0;
 	}
@@ -563,8 +567,10 @@ static int ab8500_charger_get_usb_current(struct ab8500_charger *di)
 	/* Only measure current if the charger is online */
 	if (di->usb.charger_online) {
 		ret = iio_read_channel_processed(di->adc_usb_charger_c, &ich);
-		if (ret < 0)
+		if (ret < 0) {
 			dev_err(di->dev, "%s ADC conv failed,\n", __func__);
+			return ret;
+		}
 	} else {
 		ich = 0;
 	}
@@ -586,8 +592,10 @@ static int ab8500_charger_get_ac_current(struct ab8500_charger *di)
 	/* Only measure current if the charger is online */
 	if (di->ac.charger_online) {
 		ret = iio_read_channel_processed(di->adc_main_charger_c, &ich);
-		if (ret < 0)
+		if (ret < 0) {
 			dev_err(di->dev, "%s ADC conv failed,\n", __func__);
+			return ret;
+		}
 	} else {
 		ich = 0;
 	}