iio: Add iio_device_get()

This patch add the iio_device_get() function, which increases the reference
count of a iio device. The matching function to decrease the reference count -
iio_device_put() - already exists.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/iio/iio.h

@@ -438,6 +438,17 @@ static inline struct iio_dev *dev_to_iio_dev(struct device *dev)
 	return container_of(dev, struct iio_dev, dev);
 }
 
+/**
+ * iio_device_get() - increment reference count for the device
+ * @indio_dev: IIO device structure
+ *
+ * Returns: The passed IIO device
+ **/
+static inline struct iio_dev *iio_device_get(struct iio_dev *indio_dev)
+{
+	return indio_dev ? dev_to_iio_dev(get_device(&indio_dev->dev)) : NULL;
+}
+
 /* Can we make this smaller? */
 #define IIO_ALIGN L1_CACHE_BYTES
 /**