libcamera: Handle request completion explicitly in pipeline handlers

Request complete by themselves when all the buffers they contain have
completed, connecting the buffer's completed signal to be notified of
buffer completion. While this works for now, it prevents pipelines from
delaying request completion until all metadata is available, and makes
it impossible to ensure that requests complete in the order they are
queued.

To fix this, make request completion handling explicit in pipeline
handlers. The base PipelineHandler class is extended with
implementations of the queueRequest() and stop() methods and gets new
completeBuffer() and completeRequest() methods to help pipeline handlers
tracking requests and buffers.

The three existing pipeline handlers connect the bufferReady signal of
their capture video node to a slot of their respective camera data
instance, where they use the PipelineHandler helpers to notify buffer
and request completion. Request completion is handled synchronously with
buffer completion as the pipeline handlers don't need to support more
advanced use cases, but this paves the road for future work.

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

1 files changed, 11 insertions, 19 deletions

diff --git a/src/libcamera/request.cpp b/src/libcamera/request.cpp
index cb170930..e0e77e97 100644
--- a/src/libcamera/request.cpp
+++ b/src/libcamera/request.cpp
@@ -113,7 +113,6 @@ int Request::prepare()
 {
 	for (auto const &pair : bufferMap_) {
 		Buffer *buffer = pair.second;
-		buffer->completed.connect(this, &Request::bufferCompleted);
 		pending_.insert(buffer);
 	}
 
@@ -133,31 +132,24 @@ void Request::complete(Status status)
 }
 
 /**
- * \brief Slot for the buffer completed signal
+ * \brief Complete a buffer for the request
+ * \param[in] buffer The buffer that has completed
  *
- * The bufferCompleted method serves as slot where to connect the
- * Buffer::completed signal that is emitted when a buffer has available
- * data.
+ * A request tracks the status of all buffers it contains through a set of
+ * pending buffers. This function removes the \a buffer from the set to mark it
+ * as complete. All buffers associate with the request shall be marked as
+ * complete by calling this function once and once only before reporting the
+ * request as complete with the complete() method.
  *
- * The request completes when all the buffers it contains are ready to be
- * presented to the application. It then emits the Camera::requestCompleted
- * signal and is automatically deleted.
+ * \return True if all buffers contained in the request have completed, false
+ * otherwise
  */
-void Request::bufferCompleted(Buffer *buffer)
+bool Request::completeBuffer(Buffer *buffer)
 {
-	buffer->completed.disconnect(this, &Request::bufferCompleted);
-
 	int ret = pending_.erase(buffer);
 	ASSERT(ret == 1);
 
-	if (!pending_.empty())
-		return;
-
-	complete(RequestComplete);
-
-	std::map<Stream *, Buffer *> buffers(std::move(bufferMap_));
-	camera_->requestCompleted.emit(this, buffers);
-	delete this;
+	return pending_.empty();
 }
 
 } /* namespace libcamera */