linux-kernel - [PATCH v1 06/17] iio: chemical: bme680: Add mutexes to guard read/write to device

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Date: Mon, 27 May 2024 20:37:54 +0200
From: Vasileios Amoiridis <vassilisamir@...il.com>
To: jic23@...nel.org,
	lars@...afoo.de
Cc: himanshujha199640@...il.com,
	linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Vasileios Amoiridis <vassilisamir@...il.com>
Subject: [PATCH v1 06/17] iio: chemical: bme680: Add mutexes to guard read/write to device

Add mutexes in the {read/write}_raw() functions of the device to
guard the read/write of data from/to the device. This is necessary
because for any operation other than temperature, multiple reads
need to take place from the device. Even though regmap has a locking
by itself, it won't protect us from multiple applications trying to
read at the same time temperature and pressure since the pressure
reading includes an internal temperature reading and there is nothing
to ensure that this temperature+pressure reading will happen
sequentially without any other operation interfering in the meantime.

Signed-off-by: Vasileios Amoiridis <vassilisamir@...il.com>
---
 drivers/iio/chemical/bme680_core.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/iio/chemical/bme680_core.c b/drivers/iio/chemical/bme680_core.c
index 8b42c4716412..2ef3fc7effc6 100644
--- a/drivers/iio/chemical/bme680_core.c
+++ b/drivers/iio/chemical/bme680_core.c
@@ -10,6 +10,7 @@
  */
 #include <linux/acpi.h>
 #include <linux/bitfield.h>
+#include <linux/cleanup.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/module.h>
@@ -52,6 +53,7 @@ struct bme680_calib {
 struct bme680_data {
 	struct regmap *regmap;
 	struct bme680_calib bme680;
+	struct mutex lock;
 	u8 oversampling_temp;
 	u8 oversampling_press;
 	u8 oversampling_humid;
@@ -806,6 +808,8 @@ static int bme680_read_raw(struct iio_dev *indio_dev,
 {
 	struct bme680_data *data = iio_priv(indio_dev);
 
+	guard(mutex)(&data->lock);
+
 	switch (mask) {
 	case IIO_CHAN_INFO_PROCESSED:
 		switch (chan->type) {
@@ -850,6 +854,8 @@ static int bme680_write_raw(struct iio_dev *indio_dev,
 {
 	struct bme680_data *data = iio_priv(indio_dev);
 
+	guard(mutex)(&data->lock);
+
 	if (val2 != 0)
 		return -EINVAL;
 
@@ -946,6 +952,7 @@ int bme680_core_probe(struct device *dev, struct regmap *regmap,
 		name = bme680_match_acpi_device(dev);
 
 	data = iio_priv(indio_dev);
+	mutex_init(&data->lock);
 	dev_set_drvdata(dev, indio_dev);
 	data->regmap = regmap;
 	indio_dev->name = name;
-- 
2.25.1