libcamera, android, cam, gstreamer, qcam, v4l2: Reuse Request

Allow reuse of the Request object by implementing reuse(). This means
the applications now have the responsibility of freeing the Request
objects, so make all libcamera users (cam, qcam, v4l2-compat, gstreamer,
android) do so.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

2 files changed, 43 insertions, 9 deletions

diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
index fb76077f..9590ab72 100644
--- a/src/libcamera/camera.cpp
+++ b/src/libcamera/camera.cpp
@@ -847,21 +847,22 @@ int Camera::configure(CameraConfiguration *config)
  * handler, and is completely opaque to libcamera.
  *
  * The ownership of the returned request is passed to the caller, which is
- * responsible for either queueing the request or deleting it.
+ * responsible for deleting it. The request may be deleted in the completion
+ * handler, or reused after resetting its state with Request::reuse().
  *
  * \context This function is \threadsafe. It may only be called when the camera
  * is in the Configured or Running state as defined in \ref camera_operation.
  *
  * \return A pointer to the newly created request, or nullptr on error
  */
-Request *Camera::createRequest(uint64_t cookie)
+std::unique_ptr<Request> Camera::createRequest(uint64_t cookie)
 {
 	int ret = p_->isAccessAllowed(Private::CameraConfigured,
 				      Private::CameraRunning);
 	if (ret < 0)
 		return nullptr;
 
-	return new Request(this, cookie);
+	return std::make_unique<Request>(this, cookie);
 }
 
 /**
@@ -877,9 +878,6 @@ Request *Camera::createRequest(uint64_t cookie)
  * Once the request has been queued, the camera will notify its completion
  * through the \ref requestCompleted signal.
  *
- * Ownership of the request is transferred to the camera. It will be deleted
- * automatically after it completes.
- *
  * \context This function is \threadsafe. It may only be called when the camera
  * is in the Running state as defined in \ref camera_operation.
  *
@@ -988,13 +986,11 @@ int Camera::stop()
  * \param[in] request The request that has completed
  *
  * This function is called by the pipeline handler to notify the camera that
- * the request has completed. It emits the requestCompleted signal and deletes
- * the request.
+ * the request has completed. It emits the requestCompleted signal.
  */
 void Camera::requestComplete(Request *request)
 {
 	requestCompleted.emit(request);
-	delete request;
 }
 
 } /* namespace libcamera */
diff --git a/src/libcamera/request.cpp b/src/libcamera/request.cpp
index 60b30692..ae8b1660 100644
--- a/src/libcamera/request.cpp
+++ b/src/libcamera/request.cpp
@@ -38,6 +38,15 @@ LOG_DEFINE_CATEGORY(Request)
  */
 
 /**
+ * \enum Request::ReuseFlag
+ * Flags to control the behavior of Request::reuse()
+ * \var Request::Default
+ * Don't reuse buffers
+ * \var Request::ReuseBuffers
+ * Reuse the buffers that were previously added by addBuffer()
+ */
+
+/**
  * \typedef Request::BufferMap
  * \brief A map of Stream to FrameBuffer pointers
  */
@@ -86,6 +95,35 @@ Request::~Request()
 }
 
 /**
+ * \brief Reset the request for reuse
+ * \param[in] flags Indicate whether or not to reuse the buffers
+ *
+ * Reset the status and controls associated with the request, to allow it to
+ * be reused and requeued without destruction. This function shall be called
+ * prior to queueing the request to the camera, in lieu of constructing a new
+ * request. The application can reuse the buffers that were previously added
+ * to the request via addBuffer() by setting \a flags to ReuseBuffers.
+ */
+void Request::reuse(ReuseFlag flags)
+{
+	pending_.clear();
+	if (flags & ReuseBuffers) {
+		for (auto pair : bufferMap_) {
+			pair.second->request_ = this;
+			pending_.insert(pair.second);
+		}
+	} else {
+		bufferMap_.clear();
+	}
+
+	status_ = RequestPending;
+	cancelled_ = false;
+
+	controls_->clear();
+	metadata_->clear();
+}
+
+/**
  * \fn Request::controls()
  * \brief Retrieve the request's ControlList
  *