libcamera: pipeline: Introduce stopDevice()

Since a queue of waiting Requests has been introduced, not all Requests
queued to the PipelineHandler are immediately queued to the device.

As a Camera can be stopped at any time, it is required to complete the
waiting requests after the ones queued to the device had been completed.

Introduce a pure virtual PipelineHandler::stopDevice() function to be
implemented by pipeline handlers and make the PipelineHandler::stop()
function call it before completing pending requests.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/libcamera/pipeline_handler.cpp

@@ -267,8 +267,7 @@ void PipelineHandler::unlock()
  */
 
 /**
- * \fn PipelineHandler::stop()
- * \brief Stop capturing from all running streams
+ * \brief Stop capturing from all running streams and cancel pending requests
  * \param[in] camera The camera to stop
  *
  * This function stops capturing and processing requests immediately. All
@@ -276,6 +275,33 @@ void PipelineHandler::unlock()
  *
  * \context This function is called from the CameraManager thread.
  */
+void PipelineHandler::stop(Camera *camera)
+{
+	/* Stop the pipeline handler and let the queued requests complete. */
+	stopDevice(camera);
+
+	/* Cancel and signal as complete all waiting requests. */
+	while (!waitingRequests_.empty()) {
+		Request *request = waitingRequests_.front();
+		waitingRequests_.pop();
+
+		request->_d()->cancel();
+		completeRequest(request);
+	}
+
+	/* Make sure no requests are pending. */
+	Camera::Private *data = camera->_d();
+	ASSERT(data->queuedRequests_.empty());
+}
+
+/**
+ * \fn PipelineHandler::stopDevice()
+ * \brief Stop capturing from all running streams
+ * \param[in] camera The camera to stop
+ *
+ * This function stops capturing and processing requests immediately. All
+ * pending requests are cancelled and complete immediately in an error state.
+ */
 
 /**
  * \brief Determine if the camera has any requests pending