iio: adc: ad7292: use devm_regulator_get_enable_read_voltage

This makes use of the new devm_regulator_get_enable_read_voltage()
function to reduce boilerplate code.
Signed-off-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://patch.msgid.link/20240612-iio-adc-ref-supply-refactor-v2-3-fa622e7354e9@baylibre.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad7292.c

@@ -17,6 +17,8 @@
 
 #define ADI_VENDOR_ID 0x0018
 
+#define AD7292_INTERNAL_REF_MV 1250
+
 /* AD7292 registers definition */
 #define AD7292_REG_VENDOR_ID		0x00
 #define AD7292_REG_CONF_BANK		0x05
@@ -79,7 +81,6 @@ static const struct iio_chan_spec ad7292_channels_diff[] = {
 
 struct ad7292_state {
 	struct spi_device *spi;
-	struct regulator *reg;
 	unsigned short vref_mv;
 
 	__be16 d16 __aligned(IIO_DMA_MINALIGN);
@@ -250,13 +251,6 @@ static const struct iio_info ad7292_info = {
 	.read_raw = ad7292_read_raw,
 };
 
-static void ad7292_regulator_disable(void *data)
-{
-	struct ad7292_state *st = data;
-
-	regulator_disable(st->reg);
-}
-
 static int ad7292_probe(struct spi_device *spi)
 {
 	struct ad7292_state *st;
@@ -277,29 +271,11 @@ static int ad7292_probe(struct spi_device *spi)
 		return -EINVAL;
 	}
 
-	st->reg = devm_regulator_get_optional(&spi->dev, "vref");
-	if (!IS_ERR(st->reg)) {
-		ret = regulator_enable(st->reg);
-		if (ret) {
-			dev_err(&spi->dev,
-				"Failed to enable external vref supply\n");
-			return ret;
-		}
-
-		ret = devm_add_action_or_reset(&spi->dev,
-					       ad7292_regulator_disable, st);
-		if (ret)
-			return ret;
-
-		ret = regulator_get_voltage(st->reg);
-		if (ret < 0)
-			return ret;
+	ret = devm_regulator_get_enable_read_voltage(&spi->dev, "vref");
+	if (ret < 0 && ret != -ENODEV)
+		return ret;
 
-		st->vref_mv = ret / 1000;
-	} else {
-		/* Use the internal voltage reference. */
-		st->vref_mv = 1250;
-	}
+	st->vref_mv = ret == -ENODEV ? AD7292_INTERNAL_REF_MV : ret / 1000;
 
 	indio_dev->name = spi_get_device_id(spi)->name;
 	indio_dev->modes = INDIO_DIRECT_MODE;