[PATCH 06/10] iio: dac: ad5686: acquire lock when doing powerdown control

[Rodrigo Alencar via B4 Relay]

From: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>

Protect access of pwr_down_mode and pwr_down_mask fields with existing
mutex lock. This issue exists since the ad5686 driver was first
introduced. Acquire mutex with guard(mutex)() throughout for consistency,
which allows for early returns, facilitating the review of further
changes.

Fixes: c2f37c8dcadc ("iio: dac: New driver for AD5686R, AD5685R, AD5684R Digital to analog converters")
Signed-off-by: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>
---
 drivers/iio/dac/ad5686.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/iio/dac/ad5686.c b/drivers/iio/dac/ad5686.c
index 843e425f656f..c7d5ee344a6f 100644
--- a/drivers/iio/dac/ad5686.c
+++ b/drivers/iio/dac/ad5686.c
@@ -45,6 +45,8 @@ static int ad5686_get_powerdown_mode(struct iio_dev *indio_dev,
 {
 	struct ad5686_state *st = iio_priv(indio_dev);
 
+	guard(mutex)(&st->lock);
+
 	return ((st->pwr_down_mode >> (chan->channel * 2)) & 0x3) - 1;
 }
 
@@ -54,6 +56,7 @@ static int ad5686_set_powerdown_mode(struct iio_dev *indio_dev,
 {
 	struct ad5686_state *st = iio_priv(indio_dev);
 
+	guard(mutex)(&st->lock);
 	st->pwr_down_mode &= ~(0x3 << (chan->channel * 2));
 	st->pwr_down_mode |= ((mode + 1) << (chan->channel * 2));
 
@@ -72,6 +75,8 @@ static ssize_t ad5686_read_dac_powerdown(struct iio_dev *indio_dev,
 {
 	struct ad5686_state *st = iio_priv(indio_dev);
 
+	guard(mutex)(&st->lock);
+
 	return sysfs_emit(buf, "%d\n", !!(st->pwr_down_mask &
 				       (0x3 << (chan->channel * 2))));
 }
@@ -92,6 +97,8 @@ static ssize_t ad5686_write_dac_powerdown(struct iio_dev *indio_dev,
 	if (ret)
 		return ret;
 
+	guard(mutex)(&st->lock);
+
 	if (readin)
 		st->pwr_down_mask |= (0x3 << (chan->channel * 2));
 	else
@@ -138,11 +145,11 @@ static int ad5686_read_raw(struct iio_dev *indio_dev,
 	struct ad5686_state *st = iio_priv(indio_dev);
 	int ret;
 
+	guard(mutex)(&st->lock);
+
 	switch (m) {
 	case IIO_CHAN_INFO_RAW:
-		mutex_lock(&st->lock);
 		ret = st->read(st, chan->address);
-		mutex_unlock(&st->lock);
 		if (ret < 0)
 			return ret;
 		*val = (ret >> chan->scan_type.shift) &
@@ -163,25 +170,19 @@ static int ad5686_write_raw(struct iio_dev *indio_dev,
 			    long mask)
 {
 	struct ad5686_state *st = iio_priv(indio_dev);
-	int ret;
+
+	guard(mutex)(&st->lock);
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 		if (val > (1 << chan->scan_type.realbits) || val < 0)
 			return -EINVAL;
 
-		mutex_lock(&st->lock);
-		ret = st->write(st,
-				AD5686_CMD_WRITE_INPUT_N_UPDATE_N,
-				chan->address,
-				val << chan->scan_type.shift);
-		mutex_unlock(&st->lock);
-		break;
+		return st->write(st, AD5686_CMD_WRITE_INPUT_N_UPDATE_N,
+				 chan->address, val << chan->scan_type.shift);
 	default:
-		ret = -EINVAL;
+		return -EINVAL;
 	}
-
-	return ret;
 }
 
 static const struct iio_info ad5686_info = {

-- 
2.43.0