iio: adc: ad7944: simplify adi,spi-mode property parsing

This simplifies the adi,spi-mode property parsing by using
device_property_match_property_string() instead of two separate
functions. Also, the error return value is now more informative
in cases where there was a problem parsing the property.
Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20240325-ad7944-cleanups-v3-1-3a19120cdd06@baylibre.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad7944.c

@@ -366,7 +366,6 @@ static int ad7944_probe(struct spi_device *spi)
 	struct ad7944_adc *adc;
 	bool have_refin = false;
 	struct regulator *ref;
-	const char *str_val;
 	int ret;
 
 	indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
@@ -382,17 +381,17 @@ static int ad7944_probe(struct spi_device *spi)
 
 	adc->timing_spec = chip_info->timing_spec;
 
-	if (device_property_read_string(dev, "adi,spi-mode", &str_val) == 0) {
-		ret = sysfs_match_string(ad7944_spi_modes, str_val);
-		if (ret < 0)
-			return dev_err_probe(dev, -EINVAL,
-					     "unsupported adi,spi-mode\n");
-
-		adc->spi_mode = ret;
-	} else {
-		/* absence of adi,spi-mode property means default mode */
+	ret = device_property_match_property_string(dev, "adi,spi-mode",
+						    ad7944_spi_modes,
+						    ARRAY_SIZE(ad7944_spi_modes));
+	/* absence of adi,spi-mode property means default mode */
+	if (ret == -EINVAL)
 		adc->spi_mode = AD7944_SPI_MODE_DEFAULT;
-	}
+	else if (ret < 0)
+		return dev_err_probe(dev, ret,
+				     "getting adi,spi-mode property failed\n");
+	else
+		adc->spi_mode = ret;
 
 	if (adc->spi_mode == AD7944_SPI_MODE_CHAIN)
 		return dev_err_probe(dev, -EINVAL,