Error path in ADC reading function can be slighly simplified using the
guard(mutex).

Use guard(mutex) and document the mutex purpose.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>

---
Revision history:
v1 => v2:
 - Protect the shared message data
 - Add message data protection to the mutex doc
 - Reword the commit message
---
 drivers/iio/adc/ti-adc128s052.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/adc/ti-adc128s052.c b/drivers/iio/adc/ti-adc128s052.c
index bef2d29c06af..a15b75fc067e 100644
--- a/drivers/iio/adc/ti-adc128s052.c
+++ b/drivers/iio/adc/ti-adc128s052.c
@@ -9,6 +9,7 @@
  * https://www.ti.com/lit/ds/symlink/adc124s021.pdf
  */
 
+#include <linux/cleanup.h>
 #include <linux/err.h>
 #include <linux/iio/iio.h>
 #include <linux/mod_devicetable.h>
@@ -26,6 +27,10 @@ struct adc128 {
 	struct spi_device *spi;
 
 	struct regulator *reg;
+	/*
+	 * Serialize the SPI 'write-channel + read data' accesses and protect
+	 * the shared buffer.
+	 */
 	struct mutex lock;
 
 	union {
@@ -39,19 +44,16 @@ static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
 	int ret;
 	char *msg = &adc->tx_buffer[0];
 
-	mutex_lock(&adc->lock);
+	guard(mutex)(&adc->lock);
 
 	msg[0] = channel << 3;
 	msg[1] = 0;
 
 	ret = spi_write(adc->spi, msg, sizeof(adc->tx_buffer));
-	if (ret < 0) {
-		mutex_unlock(&adc->lock);
+	if (ret < 0)
 		return ret;
-	}
 
 	ret = spi_read(adc->spi, &adc->rx_buffer, 2);
-	mutex_unlock(&adc->lock);
 	if (ret < 0)
 		return ret;
 
-- 
2.49.0