[PATCH v4 1/2] staging: iio: adc: ad7816: Serialize SPI read operations

[Abdelnasser Hussein <abdelnasserhussein11@gmail.com>]

Add a mutex to serialize SPI read operations and prevent data corruption. Used guard(mutex) and devm_mutex_init() for safer and automatic cleanup.
Signed-off-by: Abdelnasser Hussein <abdelnasserhussein11@gmail.com>
---
 drivers/staging/iio/adc/ad7816.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/iio/adc/ad7816.c b/drivers/staging/iio/adc/ad7816.c
index 0e32a2295990..ab80b3a889bb 100644
--- a/drivers/staging/iio/adc/ad7816.c
+++ b/drivers/staging/iio/adc/ad7816.c
@@ -14,6 +14,8 @@
 #include <linux/list.h>
 #include <linux/spi/spi.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/cleanup.h>
 
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
@@ -65,7 +67,8 @@ static int ad7816_spi_read(struct ad7816_chip_info *chip, u16 *data)
 {
 	struct spi_device *spi_dev = chip->spi_dev;
 	int ret;
-	__be16 buf;
+
+	guard(mutex)(&chip->lock);
 
 	gpiod_set_value(chip->rdwr_pin, 1);
 	gpiod_set_value(chip->rdwr_pin, 0);
@@ -360,6 +363,10 @@ static int ad7816_probe(struct spi_device *spi_dev)
 		return -ENOMEM;
 	chip = iio_priv(indio_dev);
 
+	ret = devm_mutex_init(&spi_dev->dev, &chip->lock);
+	if (ret)
+		return ret;
+
 	chip->spi_dev = spi_dev;
 	for (i = 0; i <= AD7816_CS_MAX; i++)
 		chip->oti_data[i] = 203;
-- 
2.54.0