iio: dht11: Add locking

Make sure that the read function is not interrupted...
Signed-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Harald Geyer <harald@ccbib.org>
Reviewed-by: Sanjeev Sharma <sanjeev_sharma@mentor.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/humidity/dht11.c

@@ -29,6 +29,7 @@
 #include <linux/wait.h>
 #include <linux/bitops.h>
 #include <linux/completion.h>
+#include <linux/mutex.h>
 #include <linux/delay.h>
 #include <linux/gpio.h>
 #include <linux/of_gpio.h>
@@ -57,6 +58,7 @@ struct dht11 {
 	int				irq;
 
 	struct completion		completion;
+	struct mutex			lock;
 
 	s64				timestamp;
 	int				temperature;
@@ -145,6 +147,7 @@ static int dht11_read_raw(struct iio_dev *iio_dev,
 	struct dht11 *dht11 = iio_priv(iio_dev);
 	int ret;
 
+	mutex_lock(&dht11->lock);
 	if (dht11->timestamp + DHT11_DATA_VALID_TIME < iio_get_time_ns()) {
 		reinit_completion(&dht11->completion);
 
@@ -185,6 +188,7 @@ static int dht11_read_raw(struct iio_dev *iio_dev,
 		ret = -EINVAL;
 err:
 	dht11->num_edges = -1;
+	mutex_unlock(&dht11->lock);
 	return ret;
 }
 
@@ -268,6 +272,7 @@ static int dht11_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, iio);
 
 	init_completion(&dht11->completion);
+	mutex_init(&dht11->lock);
 	iio->name = pdev->name;
 	iio->dev.parent = &pdev->dev;
 	iio->info = &dht11_iio_info;