iio: adc: ad799x: use iio helper function to guarantee direct mode

Replace the code that guarantees the device stays in direct mode
with iio_device_claim_direct_mode() which does same.
Signed-off-by: Alison Schofield <amsfield22@gmail.com>
Acked-by: Daniel Baluta <daniel.baluta@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/ad799x.c

@@ -282,12 +282,11 @@ static int ad799x_read_raw(struct iio_dev *indio_dev,
 
 	switch (m) {
 	case IIO_CHAN_INFO_RAW:
-		mutex_lock(&indio_dev->mlock);
-		if (iio_buffer_enabled(indio_dev))
-			ret = -EBUSY;
-		else
+		ret = iio_device_claim_direct_mode(indio_dev);
+		if (ret)
+			return ret;
 		ret = ad799x_scan_direct(st, chan->scan_index);
-		mutex_unlock(&indio_dev->mlock);
+		iio_device_release_direct_mode(indio_dev);
 
 		if (ret < 0)
 			return ret;
@@ -395,11 +394,9 @@ static int ad799x_write_event_config(struct iio_dev *indio_dev,
 	struct ad799x_state *st = iio_priv(indio_dev);
 	int ret;
 
-	mutex_lock(&indio_dev->mlock);
-	if (iio_buffer_enabled(indio_dev)) {
-		ret = -EBUSY;
-		goto done;
-	}
+	ret = iio_device_claim_direct_mode(indio_dev);
+	if (ret)
+		return ret;
 
 	if (state)
 		st->config |= BIT(chan->scan_index) << AD799X_CHANNEL_SHIFT;
@@ -412,10 +409,7 @@ static int ad799x_write_event_config(struct iio_dev *indio_dev,
 		st->config &= ~AD7998_ALERT_EN;
 
 	ret = ad799x_write_config(st, st->config);
-
-done:
-	mutex_unlock(&indio_dev->mlock);
-
+	iio_device_release_direct_mode(indio_dev);
 	return ret;
 }