libcamera: ipu3: Accept an empty roles list

The IPU3 pipeline handler that does not support receiving an empty list
of roles at generateConfiguration() time. This contradicts the camera
API which allows application to generate empty CameraConfiguration to
be later manually filled.

Fix this by returning an empty CameraConfiguration if the list of
requested roles is empty. While at it, align the style with the other
pipeline handlers.

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

src/libcamera/pipeline/ipu3/ipu3.cpp

@@ -292,14 +292,15 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
 	const StreamRoles &roles)
 {
 	IPU3CameraData *data = cameraData(camera);
-	IPU3CameraConfiguration *config;
+	IPU3CameraConfiguration *config = new IPU3CameraConfiguration(camera, data);
 	std::set<Stream *> streams = {
 		&data->outStream_,
 		&data->vfStream_,
 		&data->rawStream_,
 	};
 
-	config = new IPU3CameraConfiguration(camera, data);
+	if (roles.empty())
+		return config;
 
 	for (const StreamRole role : roles) {
 		StreamConfiguration cfg = {};