[PATCH] iio: temperature: mlx90614: use guard(mutex) for EEPROM access locking

[Luiz Mugnaini]

From: Luiz Mugnaini <luizmugnaini em usp.br>

Replace mutex_lock()/mutex_unlock() pairs with guard(mutex) from
cleanup.h for cleaner and safer mutex handling. The lock protects
EEPROM access across five call sites in mlx90614_read_raw(),
mlx90614_write_raw(), and mlx90614_sleep().

In all cases, the code between mutex_unlock() and the end of scope
is either trivial computation, a return statement, or a call to
mlx90614_power_put() (which only schedules a deferred autosuspend
via pm_runtime_put_autosuspend()). The slightly extended lock scope
is negligible compared to the existing hold times, which include
EEPROM write cycles with 40ms sleeps.

Signed-off-by: Luiz Mugnaini <luizmugnaini em usp.br>
---
 drivers/iio/temperature/mlx90614.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/iio/temperature/mlx90614.c b/drivers/iio/temperature/mlx90614.c
index 1ad21b73e..adf100756 100644
--- a/drivers/iio/temperature/mlx90614.c
+++ b/drivers/iio/temperature/mlx90614.c
@@ -23,6 +23,7 @@
  */
 
 #include <linux/bitfield.h>
+#include <linux/cleanup.h>
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/gpio/consumer.h>
@@ -296,10 +297,9 @@ static int mlx90614_read_raw(struct iio_dev *indio_dev,
 		if (ret < 0)
 			return ret;
 
-		mutex_lock(&data->lock);
+		guard(mutex)(&data->lock);
 		ret = i2c_smbus_read_word_data(data->client,
 					       chip_info->op_eeprom_emissivity);
-		mutex_unlock(&data->lock);
 		mlx90614_power_put(data);
 
 		if (ret < 0)
@@ -319,10 +319,9 @@ static int mlx90614_read_raw(struct iio_dev *indio_dev,
 		if (ret < 0)
 			return ret;
 
-		mutex_lock(&data->lock);
+		guard(mutex)(&data->lock);
 		ret = i2c_smbus_read_word_data(data->client,
 					       chip_info->op_eeprom_config1);
-		mutex_unlock(&data->lock);
 		mlx90614_power_put(data);
 
 		if (ret < 0)
@@ -358,10 +357,9 @@ static int mlx90614_write_raw(struct iio_dev *indio_dev,
 		if (ret < 0)
 			return ret;
 
-		mutex_lock(&data->lock);
+		guard(mutex)(&data->lock);
 		ret = mlx90614_write_word(data->client,
 					  chip_info->op_eeprom_emissivity, val);
-		mutex_unlock(&data->lock);
 		mlx90614_power_put(data);
 
 		return ret;
@@ -373,10 +371,9 @@ static int mlx90614_write_raw(struct iio_dev *indio_dev,
 		if (ret < 0)
 			return ret;
 
-		mutex_lock(&data->lock);
+		guard(mutex)(&data->lock);
 		ret = mlx90614_iir_search(data->client,
 					  val * 100 + val2 / 10000);
-		mutex_unlock(&data->lock);
 		mlx90614_power_put(data);
 
 		return ret;
@@ -476,12 +473,11 @@ static int mlx90614_sleep(struct mlx90614_data *data)
 
 	dev_dbg(&data->client->dev, "Requesting sleep");
 
-	mutex_lock(&data->lock);
+	guard(mutex)(&data->lock);
 	ret = i2c_smbus_xfer(data->client->adapter, data->client->addr,
 			     data->client->flags | I2C_CLIENT_PEC,
 			     I2C_SMBUS_WRITE, chip_info->op_sleep,
 			     I2C_SMBUS_BYTE, NULL);
-	mutex_unlock(&data->lock);
 
 	return ret;
 }
-- 
2.53.0