libcamera: pipeline_handler: Simplify request completion

libcamera guarantees that requests complete in sequence. This
requirement is currently pushed down to pipeline handlers. Three out of
four of our pipeline handlers implement that requirement based on the
sole assumption that buffers will always complete in sequeuence, while
the IPU3 pipeline handler implements a more complex logic.

It turns out that the logic can be moved to the base PipelineHandler
class with support from the Request class. Do so to simplify the
pipeline handlers.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/libcamera/pipeline/ipu3/ipu3.cpp

@@ -927,15 +927,9 @@ void IPU3CameraData::imguOutputBufferReady(Buffer *buffer)
 		/* Request not completed yet, return here. */
 		return;
 
-	/* Complete the pending requests in queueing order. */
-	while (1) {
-		request = queuedRequests_.front();
-		if (request->hasPendingBuffers())
-			break;
-
+	/* Mark the request as complete. */
 	pipe_->completeRequest(camera_, request);
 }
-}
 
 /**
  * \brief Handle buffers completion at the CIO2 output

src/libcamera/pipeline/rkisp1/rkisp1.cpp

@@ -491,9 +491,7 @@ bool PipelineHandlerRkISP1::match(DeviceEnumerator *enumerator)
 void PipelineHandlerRkISP1::bufferReady(Buffer *buffer)
 {
 	ASSERT(activeCamera_);
-
-	RkISP1CameraData *data = cameraData(activeCamera_);
-	Request *request = data->queuedRequests_.front();
+	Request *request = buffer->request();
 
 	completeBuffer(activeCamera_, request, buffer);
 	completeRequest(activeCamera_, request);

src/libcamera/pipeline/uvcvideo.cpp

@@ -382,7 +382,7 @@ int UVCCameraData::init(MediaEntity *entity)
 
 void UVCCameraData::bufferReady(Buffer *buffer)
 {
-	Request *request = queuedRequests_.front();
+	Request *request = buffer->request();
 
 	pipe_->completeBuffer(camera_, request, buffer);
 	pipe_->completeRequest(camera_, request);

src/libcamera/pipeline/vimc.cpp

@@ -376,7 +376,7 @@ int VimcCameraData::init(MediaDevice *media)
 
 void VimcCameraData::bufferReady(Buffer *buffer)
 {
-	Request *request = queuedRequests_.front();
+	Request *request = buffer->request();
 
 	pipe_->completeBuffer(camera_, request, buffer);
 	pipe_->completeRequest(camera_, request);

src/libcamera/pipeline_handler.cpp

@@ -391,8 +391,9 @@ int PipelineHandler::queueRequest(Camera *camera, Request *request)
  * This method shall be called by pipeline handlers to signal completion of the
  * \a buffer part of the \a request. It notifies applications of buffer
  * completion and updates the request's internal buffer tracking. The request
- * is not completed automatically when the last buffer completes, pipeline
- * handlers shall complete requests explicitly with completeRequest().
+ * is not completed automatically when the last buffer completes to give
+ * pipeline handlers a chance to perform any operation that may still be
+ * needed. They shall complete requests explicitly with completeRequest().
  *
  * \return True if all buffers contained in the request have completed, false
  * otherwise
@@ -413,18 +414,25 @@ bool PipelineHandler::completeBuffer(Camera *camera, Request *request,
  * request has completed. The request is deleted and shall not be accessed once
  * this method returns.
  *
- * The pipeline handler shall ensure that requests complete in the same order
- * they are submitted.
+ * This method ensures that requests will be returned to the application in
+ * submission order, the pipeline handler may call it on any complete request
+ * without any ordering constraint.
  */
 void PipelineHandler::completeRequest(Camera *camera, Request *request)
 {
-	CameraData *data = cameraData(camera);
-	ASSERT(request == data->queuedRequests_.front());
-	data->queuedRequests_.pop_front();
-
 	request->complete(Request::RequestComplete);
+
+	CameraData *data = cameraData(camera);
+
+	while (!data->queuedRequests_.empty()) {
+		request = data->queuedRequests_.front();
+		if (request->hasPendingBuffers())
+			break;
+
+		data->queuedRequests_.pop_front();
 		camera->requestComplete(request);
 	}
+}
 
 /**
  * \brief Register a camera to the camera manager and pipeline handler