iio: core: Match iio_device_claim_*() semantics and implementation

Implement iio_device_claim_buffer_mode() fully inline with the use of
__iio_dev_mode_lock(), which takes care of sparse annotations.

To completely match iio_device_claim_direct() semantics, we need to
also change iio_device_claim_buffer_mode() return semantics to usual
true/false conditional lock semantics.

Additionally, to avoid silently breaking out-of-tree drivers, rename
iio_device_claim_buffer_mode() to iio_device_claim_try_buffer_mode().

Reviewed-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Kurt Borja <kuurtb@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

1 files changed, 33 insertions, 2 deletions

diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index e263ab5eeccf..36bd14e93a75 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -706,8 +706,39 @@ static inline bool iio_device_claim_direct(struct iio_dev *indio_dev)
  */
 #define iio_device_release_direct(indio_dev) __iio_dev_mode_unlock(indio_dev)
 
-int iio_device_claim_buffer_mode(struct iio_dev *indio_dev);
-void iio_device_release_buffer_mode(struct iio_dev *indio_dev);
+/**
+ * iio_device_try_claim_buffer_mode() - Keep device in buffer mode
+ * @indio_dev:	the iio_dev associated with the device
+ *
+ * If the device is in buffer mode it is guaranteed to stay
+ * that way until iio_device_release_buffer_mode() is called.
+ *
+ * Use with iio_device_release_buffer_mode().
+ *
+ * Returns: true on success, false on failure.
+ */
+static inline bool iio_device_try_claim_buffer_mode(struct iio_dev *indio_dev)
+{
+	__iio_dev_mode_lock(indio_dev);
+
+	if (!iio_buffer_enabled(indio_dev)) {
+		__iio_dev_mode_unlock(indio_dev);
+		return false;
+	}
+
+	return true;
+}
+
+/**
+ * iio_device_release_buffer_mode() - releases claim on buffer mode
+ * @indio_dev:	the iio_dev associated with the device
+ *
+ * Release the claim. Device is no longer guaranteed to stay
+ * in buffer mode.
+ *
+ * Use with iio_device_try_claim_buffer_mode().
+ */
+#define iio_device_release_buffer_mode(indio_dev) __iio_dev_mode_unlock(indio_dev)
 
 extern const struct bus_type iio_bus_type;