[libcamera-devel] [PATCH 6/8] libcamera: camera: Add acquire() and release()

[Niklas Söderlund]

From: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
---
 include/libcamera/camera.h |  5 +++++
 src/libcamera/camera.cpp   | 35 ++++++++++++++++++++++++++++++++++-
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/include/libcamera/camera.h b/include/libcamera/camera.h
index b5d4dfe4b1f6a586..3cb1ab62b791ab87 100644
--- a/include/libcamera/camera.h
+++ b/include/libcamera/camera.h
@@ -27,12 +27,17 @@ public:
 
 	void disconnect();
 
+	int acquire();
+	void release();
+
 private:
 	explicit Camera(const std::string &name, class PipelineHandler *pipe);
 	~Camera();
 
 	std::string name_;
 	class PipelineHandler *pipe_;
+
+	bool acquired_;
 };
 
 } /* namespace libcamera */
diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
index 496fb1021c4fccf0..ee5e6dedb242a1fd 100644
--- a/src/libcamera/camera.cpp
+++ b/src/libcamera/camera.cpp
@@ -103,7 +103,7 @@ void Camera::disconnect()
 }
 
 Camera::Camera(const std::string &name, class PipelineHandler *pipe)
-	: name_(name), pipe_(pipe)
+	: name_(name), pipe_(pipe), acquired_(false)
 {
 }
 
@@ -111,4 +111,37 @@ Camera::~Camera()
 {
 }
 
+/**
+ * \brief Acquire the camera device for exclusive access
+ *
+ * After opening the device with open(), exclusive access must be obtained
+ * before performing operations that change the device state. This function is
+ * not blocking, if the device has already been acquired (by the same or another
+ * process) the -EBUSY error code is returned.
+ *
+ * Once exclusive access isn't needed anymore, the device should be released
+ * with a call to the release() function.
+ *
+ * \return 0 on success or a negative error code on error.
+ */
+int Camera::acquire()
+{
+	if (acquired_)
+		return -EBUSY;
+
+	acquired_ = true;
+	return 0;
+}
+
+/**
+ * \brief Release exclusive access to the camera device
+ *
+ * Releasing the camera device allows other users to acquire exclusive access
+ * with the acquire() function.
+ */
+void Camera::release()
+{
+	acquired_ = false;
+}
+
 } /* namespace libcamera */
-- 
2.20.1