[libcamera-devel] [PATCH v2 3/8] libcamera: pipeline_handler: Notify Request queueing failure

[Jacopo Mondi]

Capture requests are queued by the PipelineHandler base class to each
pipeline handler implementation using the virtual queueRequestDevice()
function.

However, if the pipeline handler fails to queue the request to the
hardware, the request gets silently deleted from the list of queued
ones, without notifying application of the error.

Allowing applications to know if a Request has failed to queue
by emitting the Camera::bufferCompleted and Camera::requestCompleted
signals allows them to maintain a state consistent with the one
internal to the library.

To do so, if queuing a request to the device fails, cancel the request
and emit the completion signal to report the failure to applications.

Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
---
 src/libcamera/pipeline_handler.cpp | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/libcamera/pipeline_handler.cpp b/src/libcamera/pipeline_handler.cpp
index f41b7a7b3308..260a52018a4d 100644
--- a/src/libcamera/pipeline_handler.cpp
+++ b/src/libcamera/pipeline_handler.cpp
@@ -391,6 +391,8 @@ bool PipelineHandler::hasPendingRequests(const Camera *camera) const
  * This method queues a capture request to the pipeline handler for processing.
  * The request is first added to the internal list of queued requests, and
  * then passed to the pipeline handler with a call to queueRequestDevice().
+ * If the pipeline handler fails in queuing the request to the hardware the
+ * request is immediately completed with error.
  *
  * Keeping track of queued requests ensures automatic completion of all requests
  * when the pipeline handler is stopped with stop(). Request completion shall be
@@ -409,8 +411,19 @@ void PipelineHandler::queueRequest(Request *request)
 	request->sequence_ = data->requestSequence_++;
 
 	int ret = queueRequestDevice(camera, request);
-	if (ret)
+	if (ret) {
+		/*
+		 * Cancel the request and notify completion of its buffers in
+		 * error state. Then complete the cancelled request and remove
+		 * it from the queued requests list.
+		 */
+		request->cancel();
+		for (auto bufferMap : request->buffers())
+			camera->bufferCompleted.emit(request, bufferMap.second);
+
+		camera->requestComplete(request);
 		data->queuedRequests_.remove(request);
+	}
 }
 
 /**
-- 
2.31.1