iio: adc: ad7944: 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-v2-5-fa622e7354e9@baylibre.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad7944.c

@@ -464,23 +464,17 @@ static const char * const ad7944_power_supplies[] = {
 	"avdd",	"dvdd",	"bvdd", "vio"
 };
 
-static void ad7944_ref_disable(void *ref)
-{
-	regulator_disable(ref);
-}
-
 static int ad7944_probe(struct spi_device *spi)
 {
 	const struct ad7944_chip_info *chip_info;
 	struct device *dev = &spi->dev;
 	struct iio_dev *indio_dev;
 	struct ad7944_adc *adc;
-	bool have_refin = false;
-	struct regulator *ref;
+	bool have_refin;
 	struct iio_chan_spec *chain_chan;
 	unsigned long *chain_scan_masks;
 	u32 n_chain_dev;
-	int ret;
+	int ret, ref_mv;
 
 	indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
 	if (!indio_dev)
@@ -531,47 +525,23 @@ static int ad7944_probe(struct spi_device *spi)
 	 * - external reference: REF is connected, REFIN is not connected
 	 */
 
-	ref = devm_regulator_get_optional(dev, "ref");
-	if (IS_ERR(ref)) {
-		if (PTR_ERR(ref) != -ENODEV)
-			return dev_err_probe(dev, PTR_ERR(ref),
-					     "failed to get REF supply\n");
+	ret = devm_regulator_get_enable_read_voltage(dev, "ref");
+	if (ret < 0 && ret != -ENODEV)
+		return dev_err_probe(dev, ret, "failed to get REF voltage\n");
 
-		ref = NULL;
-	}
+	ref_mv = ret == -ENODEV ? 0 : ret / 1000;
 
 	ret = devm_regulator_get_enable_optional(dev, "refin");
-	if (ret == 0)
-		have_refin = true;
-	else if (ret != -ENODEV)
-		return dev_err_probe(dev, ret,
-				     "failed to get and enable REFIN supply\n");
+	if (ret < 0 && ret != -ENODEV)
+		return dev_err_probe(dev, ret, "failed to get REFIN voltage\n");
+
+	have_refin = ret != -ENODEV;
 
-	if (have_refin && ref)
+	if (have_refin && ref_mv)
 		return dev_err_probe(dev, -EINVAL,
 				     "cannot have both refin and ref supplies\n");
 
-	if (ref) {
-		ret = regulator_enable(ref);
-		if (ret)
-			return dev_err_probe(dev, ret,
-					     "failed to enable REF supply\n");
-
-		ret = devm_add_action_or_reset(dev, ad7944_ref_disable, ref);
-		if (ret)
-			return ret;
-
-		ret = regulator_get_voltage(ref);
-		if (ret < 0)
-			return dev_err_probe(dev, ret,
-					     "failed to get REF voltage\n");
-
-		/* external reference */
-		adc->ref_mv = ret / 1000;
-	} else {
-		/* internal reference */
-		adc->ref_mv = AD7944_INTERNAL_REF_MV;
-	}
+	adc->ref_mv = ref_mv ?: AD7944_INTERNAL_REF_MV;
 
 	adc->cnv = devm_gpiod_get_optional(dev, "cnv", GPIOD_OUT_LOW);
 	if (IS_ERR(adc->cnv))