iio: pressure: ms5611: claim direct mode during oversampling changes

Driver was checking for direct mode before changing oversampling
ratios, but was not locking it.  Use the claim/release helper
functions to guarantee the device stays in direct mode while the
oversampling ratios are being updated.  Continue to use the drivers
private state lock to protect against conflicting direct mode access
of the state data.

Signed-off-by: Alison Schofield <amsfield22@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/pressure/ms5611_core.c

@@ -308,6 +308,7 @@ static int ms5611_write_raw(struct iio_dev *indio_dev,
 {
 	struct ms5611_state *st = iio_priv(indio_dev);
 	const struct ms5611_osr *osr = NULL;
+	int ret;
 
 	if (mask != IIO_CHAN_INFO_OVERSAMPLING_RATIO)
 		return -EINVAL;
@@ -321,12 +322,11 @@ static int ms5611_write_raw(struct iio_dev *indio_dev,
 	if (!osr)
 		return -EINVAL;
 
-	mutex_lock(&st->lock);
+	ret = iio_device_claim_direct_mode(indio_dev);
+	if (ret)
+		return ret;
 
-	if (iio_buffer_enabled(indio_dev)) {
-		mutex_unlock(&st->lock);
-		return -EBUSY;
-	}
+	mutex_lock(&st->lock);
 
 	if (chan->type == IIO_TEMP)
 		st->temp_osr = osr;
@@ -334,6 +334,8 @@ static int ms5611_write_raw(struct iio_dev *indio_dev,
 		st->pressure_osr = osr;
 
 	mutex_unlock(&st->lock);
+	iio_device_release_direct_mode(indio_dev);
+
 	return 0;
 }