libcamera: request: addBuffer(): Do not destroy fence on failure

Take the unique pointer to the `Fence` object by rvalue reference
so that it is not destroyed if the function returns an error code
and does not take ownership of the unique pointer.

Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>

src/libcamera/request.cpp

@@ -452,7 +452,9 @@ void Request::reuse(ReuseFlag flags)
  *
  * When a valid Fence is provided to this function, \a fence is moved to \a
  * buffer and this Request will only be queued to the device once the
- * fences of all its buffers have been correctly signalled.
+ * fences of all its buffers have been correctly signalled. Ownership of the
+ * fence will only be taken in case of success, otherwise the fence will
+ * be left unmodified.
  *
  * If the \a fence associated with \a buffer isn't signalled, the request will
  * fail after a timeout. The buffer will still contain the fence, which
@@ -468,7 +470,7 @@ void Request::reuse(ReuseFlag flags)
  * \retval -EINVAL The buffer does not reference a valid Stream
  */
 int Request::addBuffer(const Stream *stream, FrameBuffer *buffer,
-		       std::unique_ptr<Fence> fence)
+		       std::unique_ptr<Fence> &&fence)
 {
 	if (!stream) {
 		LOG(Request, Error) << "Invalid stream reference";