libcamera: request: Provide a sequence number

Provide a sequence number on Requests which are added by the pipeline
handler.

Each pipeline handler keeps a requestSequence per CameraData and
increments everytime a request is queued on that camera.

The sequence number is associated with the Request and can be utilised
for assisting with debugging, and printing the queueing sequence of in
flight requests.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

include/libcamera/internal/pipeline_handler.h

@@ -38,7 +38,7 @@ class CameraData
 {
 public:
 	explicit CameraData(PipelineHandler *pipe)
-		: pipe_(pipe)
+		: pipe_(pipe), requestSequence_(0)
 	{
 	}
 	virtual ~CameraData() = default;
@@ -48,6 +48,8 @@ public:
 	ControlInfoMap controlInfo_;
 	ControlList properties_;
 
+	uint32_t requestSequence_;
+
 private:
 	LIBCAMERA_DISABLE_COPY(CameraData)
 };

include/libcamera/request.h

@@ -50,6 +50,7 @@ public:
 	int addBuffer(const Stream *stream, FrameBuffer *buffer);
 	FrameBuffer *findBuffer(const Stream *stream) const;
 
+	uint32_t sequence() const { return sequence_; }
 	uint64_t cookie() const { return cookie_; }
 	Status status() const { return status_; }
 
@@ -71,6 +72,7 @@ private:
 	BufferMap bufferMap_;
 	std::unordered_set<FrameBuffer *> pending_;
 
+	uint32_t sequence_;
 	const uint64_t cookie_;
 	Status status_;
 	bool cancelled_;

src/libcamera/pipeline_handler.cpp

@@ -382,6 +382,8 @@ int PipelineHandler::queueRequest(Request *request)
 	CameraData *data = cameraData(camera);
 	data->queuedRequests_.push_back(request);
 
+	request->sequence_ = data->requestSequence_++;
+
 	int ret = queueRequestDevice(camera, request);
 	if (ret)
 		data->queuedRequests_.remove(request);

src/libcamera/request.cpp

@@ -72,8 +72,8 @@ LOG_DEFINE_CATEGORY(Request)
  *
  */
 Request::Request(Camera *camera, uint64_t cookie)
-	: camera_(camera), cookie_(cookie), status_(RequestPending),
-	  cancelled_(false)
+	: camera_(camera), sequence_(0), cookie_(cookie),
+	  status_(RequestPending), cancelled_(false)
 {
 	/**
 	 * \todo Should the Camera expose a validator instance, to avoid
@@ -126,6 +126,7 @@ void Request::reuse(ReuseFlag flags)
 		bufferMap_.clear();
 	}
 
+	sequence_ = 0;
 	status_ = RequestPending;
 	cancelled_ = false;
 
@@ -227,6 +228,23 @@ FrameBuffer *Request::findBuffer(const Stream *stream) const
  * \return The metadata associated with the request
  */
 
+/**
+ * \fn Request::sequence()
+ * \brief Retrieve the sequence number for the request
+ *
+ * When requests are queued, they are given a sequential number to track the
+ * order in which requests are queued to a camera. This number counts all
+ * requests given to a camera through its lifetime, and is not reset to zero
+ * between camera stop/start sequences.
+ *
+ * It can be used to support debugging and identifying the flow of requests
+ * through a pipeline, but does not guarantee to represent the sequence number
+ * of any images in the stream. The sequence number is stored as an unsigned
+ * integer and will wrap when overflowed.
+ *
+ * \return The request sequence number
+ */
+
 /**
  * \fn Request::cookie()
  * \brief Retrieve the cookie set when the request was created