libcamera: camera: Return a pointer from generateConfiguration()

To prepare for specialising the CameraConfiguration class in pipeline
handlers, return a pointer to a camera configuration instead of a
reference from Camera::generateConfiguration(). The camera configuration
always needs to be allocated from the pipeline handler, and its
ownership is passed to the application.

For symmetry, change Camera::configure() to take a CameraConfiguration
pointer instead of a reference. This aligns with our coding practice of
passing parameters that are modified by the callee by pointer.

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

src/cam/main.cpp

@@ -85,15 +85,13 @@ static int parseOptions(int argc, char *argv[])
 	return 0;
 }
 
-static int prepareCameraConfig(CameraConfiguration *config)
+static std::unique_ptr<CameraConfiguration> prepareCameraConfig()
 {
 	StreamRoles roles;
 
 	/* If no configuration is provided assume a single video stream. */
-	if (!options.isSet(OptStream)) {
-		*config = camera->generateConfiguration({ StreamRole::VideoRecording });
-		return 0;
-	}
+	if (!options.isSet(OptStream))
+		return camera->generateConfiguration({ StreamRole::VideoRecording });
 
 	const std::vector<OptionValue> &streamOptions =
 		options[OptStream].toArray();
@@ -113,23 +111,22 @@ static int prepareCameraConfig(CameraConfiguration *config)
 		} else {
 			std::cerr << "Unknown stream role "
 				  << conf["role"].toString() << std::endl;
-			return -EINVAL;
+			return nullptr;
 		}
 	}
 
-	*config = camera->generateConfiguration(roles);
-
-	if (!config->isValid()) {
+	std::unique_ptr<CameraConfiguration> config = camera->generateConfiguration(roles);
+	if (!config || !config->isValid()) {
 		std::cerr << "Failed to get default stream configuration"
 			  << std::endl;
-		return -EINVAL;
+		return nullptr;
 	}
 
 	/* Apply configuration explicitly requested. */
 	unsigned int i = 0;
 	for (auto const &value : streamOptions) {
 		KeyValueParser::Options conf = value.toKeyValues();
-		StreamConfiguration &cfg = (*config)[i++];
+		StreamConfiguration &cfg = config->at(i++);
 
 		if (conf.isSet("width"))
 			cfg.size.width = conf["width"];
@@ -142,7 +139,7 @@ static int prepareCameraConfig(CameraConfiguration *config)
 			cfg.pixelFormat = conf["pixelformat"];
 	}
 
-	return 0;
+	return config;
 }
 
 static void requestComplete(Request *request, const std::map<Stream *, Buffer *> &buffers)
@@ -191,16 +188,15 @@ static void requestComplete(Request *request, const std::map<Stream *, Buffer *>
 
 static int capture()
 {
-	CameraConfiguration config;
 	int ret;
 
-	ret = prepareCameraConfig(&config);
-	if (ret) {
+	std::unique_ptr<CameraConfiguration> config = prepareCameraConfig();
+	if (!config) {
 		std::cout << "Failed to prepare camera configuration" << std::endl;
-		return ret;
+		return -EINVAL;
 	}
 
-	ret = camera->configure(config);
+	ret = camera->configure(config.get());
 	if (ret < 0) {
 		std::cout << "Failed to configure camera" << std::endl;
 		return ret;
@@ -208,8 +204,8 @@ static int capture()
 
 	streamInfo.clear();
 
-	for (unsigned int index = 0; index < config.size(); ++index) {
-		StreamConfiguration &cfg = config[index];
+	for (unsigned int index = 0; index < config->size(); ++index) {
+		StreamConfiguration &cfg = config->at(index);
 		streamInfo[cfg.stream()] = "stream" + std::to_string(index);
 	}
 
@@ -224,7 +220,7 @@ static int capture()
 
 	/* Identify the stream with the least number of buffers. */
 	unsigned int nbuffers = UINT_MAX;
-	for (StreamConfiguration &cfg : config) {
+	for (StreamConfiguration &cfg : *config) {
 		Stream *stream = cfg.stream();
 		nbuffers = std::min(nbuffers, stream->bufferPool().count());
 	}
@@ -244,7 +240,7 @@ static int capture()
 		}
 
 		std::map<Stream *, Buffer *> map;
-		for (StreamConfiguration &cfg : config) {
+		for (StreamConfiguration &cfg : *config) {
 			Stream *stream = cfg.stream();
 			map[stream] = &stream->bufferPool().buffers()[i];
 		}

src/libcamera/camera.cpp

@@ -540,27 +540,37 @@ const std::set<Stream *> &Camera::streams() const
  *
  * Generate a camera configuration for a set of desired stream roles. The caller
  * specifies a list of stream roles and the camera returns a configuration
- * containing suitable streams and their suggested default configurations.
+ * containing suitable streams and their suggested default configurations. An
+ * empty list of roles is valid, and will generate an empty configuration that
+ * can be filled by the caller.
  *
- * \return A valid CameraConfiguration if the requested roles can be satisfied,
- * or a invalid one otherwise
+ * \return A CameraConfiguration if the requested roles can be satisfied, or a
+ * null pointer otherwise. The ownership of the returned configuration is
+ * passed to the caller.
  */
-CameraConfiguration
-Camera::generateConfiguration(const StreamRoles &roles)
+std::unique_ptr<CameraConfiguration> Camera::generateConfiguration(const StreamRoles &roles)
 {
-	if (disconnected_ || !roles.size() || roles.size() > streams_.size())
-		return CameraConfiguration();
+	if (disconnected_ || roles.size() > streams_.size())
+		return nullptr;
 
-	CameraConfiguration config = pipe_->generateConfiguration(this, roles);
+	CameraConfiguration *config = pipe_->generateConfiguration(this, roles);
+	if (!config) {
+		LOG(Camera, Debug)
+			<< "Pipeline handler failed to generate configuration";
+		return nullptr;
+	}
 
 	std::ostringstream msg("streams configuration:", std::ios_base::ate);
 
-	for (unsigned int index = 0; index < config.size(); ++index)
-		msg << " (" << index << ") " << config[index].toString();
+	if (config->empty())
+		msg << " empty";
+
+	for (unsigned int index = 0; index < config->size(); ++index)
+		msg << " (" << index << ") " << config->at(index).toString();
 
 	LOG(Camera, Debug) << msg.str();
 
-	return config;
+	return std::unique_ptr<CameraConfiguration>(config);
 }
 
 /**
@@ -590,7 +600,7 @@ Camera::generateConfiguration(const StreamRoles &roles)
  * \retval -EACCES The camera is not in a state where it can be configured
  * \retval -EINVAL The configuration is not valid
  */
-int Camera::configure(CameraConfiguration &config)
+int Camera::configure(CameraConfiguration *config)
 {
 	int ret;
 
@@ -600,7 +610,7 @@ int Camera::configure(CameraConfiguration &config)
 	if (!stateBetween(CameraAcquired, CameraConfigured))
 		return -EACCES;
 
-	if (!config.isValid()) {
+	if (!config->isValid()) {
 		LOG(Camera, Error)
 			<< "Can't configure camera with invalid configuration";
 		return -EINVAL;
@@ -608,8 +618,8 @@ int Camera::configure(CameraConfiguration &config)
 
 	std::ostringstream msg("configuring streams:", std::ios_base::ate);
 
-	for (unsigned int index = 0; index < config.size(); ++index) {
-		StreamConfiguration &cfg = config[index];
+	for (unsigned int index = 0; index < config->size(); ++index) {
+		StreamConfiguration &cfg = config->at(index);
 		cfg.setStream(nullptr);
 		msg << " (" << index << ") " << cfg.toString();
 	}
@@ -621,7 +631,7 @@ int Camera::configure(CameraConfiguration &config)
 		return ret;
 
 	activeStreams_.clear();
-	for (const StreamConfiguration &cfg : config) {
+	for (const StreamConfiguration &cfg : *config) {
 		Stream *stream = cfg.stream();
 		if (!stream)
 			LOG(Camera, Fatal)

src/libcamera/include/pipeline_handler.h

@@ -60,9 +60,9 @@ public:
 	bool lock();
 	void unlock();
 
-	virtual CameraConfiguration
-	generateConfiguration(Camera *camera, const StreamRoles &roles) = 0;
-	virtual int configure(Camera *camera, CameraConfiguration &config) = 0;
+	virtual CameraConfiguration *generateConfiguration(Camera *camera,
+		const StreamRoles &roles) = 0;
+	virtual int configure(Camera *camera, CameraConfiguration *config) = 0;
 
 	virtual int allocateBuffers(Camera *camera,
 				    const std::set<Stream *> &streams) = 0;

src/libcamera/pipeline/ipu3/ipu3.cpp

@@ -150,9 +150,9 @@ class PipelineHandlerIPU3 : public PipelineHandler
 public:
 	PipelineHandlerIPU3(CameraManager *manager);
 
-	CameraConfiguration
-	generateConfiguration(Camera *camera, const StreamRoles &roles) override;
-	int configure(Camera *camera, CameraConfiguration &config) override;
+	CameraConfiguration *generateConfiguration(Camera *camera,
+		const StreamRoles &roles) override;
+	int configure(Camera *camera, CameraConfiguration *config) override;
 
 	int allocateBuffers(Camera *camera,
 			    const std::set<Stream *> &streams) override;
@@ -207,12 +207,11 @@ PipelineHandlerIPU3::PipelineHandlerIPU3(CameraManager *manager)
 {
 }
 
-CameraConfiguration
-PipelineHandlerIPU3::generateConfiguration(Camera *camera,
-					   const StreamRoles &roles)
+CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
+	const StreamRoles &roles)
 {
 	IPU3CameraData *data = cameraData(camera);
-	CameraConfiguration config = {};
+	CameraConfiguration *config = new CameraConfiguration();
 	std::set<IPU3Stream *> streams = {
 		&data->outStream_,
 		&data->vfStream_,
@@ -290,21 +289,23 @@ PipelineHandlerIPU3::generateConfiguration(Camera *camera,
 			break;
 		}
 
-		if (!stream)
-			return CameraConfiguration{};
+		if (!stream) {
+			delete config;
+			return nullptr;
+		}
 
 		streams.erase(stream);
 
 		cfg.pixelFormat = V4L2_PIX_FMT_NV12;
 		cfg.bufferCount = IPU3_BUFFER_COUNT;
 
-		config.addConfiguration(cfg);
+		config->addConfiguration(cfg);
 	}
 
 	return config;
 }
 
-int PipelineHandlerIPU3::configure(Camera *camera, CameraConfiguration &config)
+int PipelineHandlerIPU3::configure(Camera *camera, CameraConfiguration *config)
 {
 	IPU3CameraData *data = cameraData(camera);
 	IPU3Stream *outStream = &data->outStream_;
@@ -316,7 +317,7 @@ int PipelineHandlerIPU3::configure(Camera *camera, CameraConfiguration &config)
 
 	outStream->active_ = false;
 	vfStream->active_ = false;
-	for (StreamConfiguration &cfg : config) {
+	for (StreamConfiguration &cfg : *config) {
 		/*
 		 * Pick a stream for the configuration entry.
 		 * \todo: This is a naive temporary implementation that will be
@@ -382,7 +383,7 @@ int PipelineHandlerIPU3::configure(Camera *camera, CameraConfiguration &config)
 		return ret;
 
 	/* Apply the format to the configured streams output devices. */
-	for (StreamConfiguration &cfg : config) {
+	for (StreamConfiguration &cfg : *config) {
 		IPU3Stream *stream = static_cast<IPU3Stream *>(cfg.stream());
 		ret = imgu->configureOutput(stream->device_, cfg);
 		if (ret)
@@ -395,13 +396,13 @@ int PipelineHandlerIPU3::configure(Camera *camera, CameraConfiguration &config)
 	 * be at least one active stream in the configuration request).
 	 */
 	if (!outStream->active_) {
-		ret = imgu->configureOutput(outStream->device_, config[0]);
+		ret = imgu->configureOutput(outStream->device_, config->at(0));
 		if (ret)
 			return ret;
 	}
 
 	if (!vfStream->active_) {
-		ret = imgu->configureOutput(vfStream->device_, config[0]);
+		ret = imgu->configureOutput(vfStream->device_, config->at(0));
 		if (ret)
 			return ret;
 	}

src/libcamera/pipeline/rkisp1/rkisp1.cpp

@@ -34,9 +34,9 @@ public:
 	PipelineHandlerRkISP1(CameraManager *manager);
 	~PipelineHandlerRkISP1();
 
-	CameraConfiguration generateConfiguration(Camera *camera,
+	CameraConfiguration *generateConfiguration(Camera *camera,
 		const StreamRoles &roles) override;
-	int configure(Camera *camera, CameraConfiguration &config) override;
+	int configure(Camera *camera, CameraConfiguration *config) override;
 
 	int allocateBuffers(Camera *camera,
 		const std::set<Stream *> &streams) override;
@@ -105,26 +105,29 @@ PipelineHandlerRkISP1::~PipelineHandlerRkISP1()
  * Pipeline Operations
  */
 
-CameraConfiguration PipelineHandlerRkISP1::generateConfiguration(Camera *camera,
+CameraConfiguration *PipelineHandlerRkISP1::generateConfiguration(Camera *camera,
 	const StreamRoles &roles)
 {
 	RkISP1CameraData *data = cameraData(camera);
-	CameraConfiguration config;
-	StreamConfiguration cfg{};
+	CameraConfiguration *config = new CameraConfiguration();
 
+	if (roles.empty())
+		return config;
+
+	StreamConfiguration cfg{};
 	cfg.pixelFormat = V4L2_PIX_FMT_NV12;
 	cfg.size = data->sensor_->resolution();
 	cfg.bufferCount = RKISP1_BUFFER_COUNT;
 
-	config.addConfiguration(cfg);
+	config->addConfiguration(cfg);
 
 	return config;
 }
 
-int PipelineHandlerRkISP1::configure(Camera *camera, CameraConfiguration &config)
+int PipelineHandlerRkISP1::configure(Camera *camera, CameraConfiguration *config)
 {
 	RkISP1CameraData *data = cameraData(camera);
-	StreamConfiguration &cfg = config[0];
+	StreamConfiguration &cfg = config->at(0);
 	CameraSensor *sensor = data->sensor_;
 	int ret;
 

src/libcamera/pipeline/uvcvideo.cpp

@@ -25,9 +25,9 @@ class PipelineHandlerUVC : public PipelineHandler
 public:
 	PipelineHandlerUVC(CameraManager *manager);
 
-	CameraConfiguration
-	generateConfiguration(Camera *camera, const StreamRoles &roles) override;
-	int configure(Camera *camera, CameraConfiguration &config) override;
+	CameraConfiguration *generateConfiguration(Camera *camera,
+		const StreamRoles &roles) override;
+	int configure(Camera *camera, CameraConfiguration *config) override;
 
 	int allocateBuffers(Camera *camera,
 			    const std::set<Stream *> &streams) override;
@@ -73,26 +73,28 @@ PipelineHandlerUVC::PipelineHandlerUVC(CameraManager *manager)
 {
 }
 
-CameraConfiguration
-PipelineHandlerUVC::generateConfiguration(Camera *camera,
-					  const StreamRoles &roles)
+CameraConfiguration *PipelineHandlerUVC::generateConfiguration(Camera *camera,
+	const StreamRoles &roles)
 {
-	CameraConfiguration config;
-	StreamConfiguration cfg;
+	CameraConfiguration *config = new CameraConfiguration();
 
+	if (roles.empty())
+		return config;
+
+	StreamConfiguration cfg{};
 	cfg.pixelFormat = V4L2_PIX_FMT_YUYV;
 	cfg.size = { 640, 480 };
 	cfg.bufferCount = 4;
 
-	config.addConfiguration(cfg);
+	config->addConfiguration(cfg);
 
 	return config;
 }
 
-int PipelineHandlerUVC::configure(Camera *camera, CameraConfiguration &config)
+int PipelineHandlerUVC::configure(Camera *camera, CameraConfiguration *config)
 {
 	UVCCameraData *data = cameraData(camera);
-	StreamConfiguration &cfg = config[0];
+	StreamConfiguration &cfg = config->at(0);
 	int ret;
 
 	V4L2DeviceFormat format = {};

src/libcamera/pipeline/vimc.cpp

@@ -25,9 +25,9 @@ class PipelineHandlerVimc : public PipelineHandler
 public:
 	PipelineHandlerVimc(CameraManager *manager);
 
-	CameraConfiguration
-	generateConfiguration(Camera *camera, const StreamRoles &roles) override;
-	int configure(Camera *camera, CameraConfiguration &config) override;
+	CameraConfiguration *generateConfiguration(Camera *camera,
+		const StreamRoles &roles) override;
+	int configure(Camera *camera, CameraConfiguration *config) override;
 
 	int allocateBuffers(Camera *camera,
 			    const std::set<Stream *> &streams) override;
@@ -73,26 +73,28 @@ PipelineHandlerVimc::PipelineHandlerVimc(CameraManager *manager)
 {
 }
 
-CameraConfiguration
-PipelineHandlerVimc::generateConfiguration(Camera *camera,
-					   const StreamRoles &roles)
+CameraConfiguration *PipelineHandlerVimc::generateConfiguration(Camera *camera,
+	const StreamRoles &roles)
 {
-	CameraConfiguration config;
-	StreamConfiguration cfg;
+	CameraConfiguration *config = new CameraConfiguration();
 
+	if (roles.empty())
+		return config;
+
+	StreamConfiguration cfg{};
 	cfg.pixelFormat = V4L2_PIX_FMT_RGB24;
 	cfg.size = { 640, 480 };
 	cfg.bufferCount = 4;
 
-	config.addConfiguration(cfg);
+	config->addConfiguration(cfg);
 
 	return config;
 }
 
-int PipelineHandlerVimc::configure(Camera *camera, CameraConfiguration &config)
+int PipelineHandlerVimc::configure(Camera *camera, CameraConfiguration *config)
 {
 	VimcCameraData *data = cameraData(camera);
-	StreamConfiguration &cfg = config[0];
+	StreamConfiguration &cfg = config->at(0);
 	int ret;
 
 	V4L2DeviceFormat format = {};

src/libcamera/pipeline_handler.cpp

@@ -233,7 +233,8 @@ void PipelineHandler::unlock()
  * the group of streams parameters.
  *
  * \return A valid CameraConfiguration if the requested roles can be satisfied,
- * or a invalid configuration otherwise
+ * or a null pointer otherwise. The ownership of the returned configuration is
+ * passed to the caller.
  */
 
 /**

src/qcam/main_window.cpp

@@ -98,13 +98,13 @@ int MainWindow::startCapture()
 	int ret;
 
 	config_ = camera_->generateConfiguration({ StreamRole::VideoRecording });
-	ret = camera_->configure(config_);
+	ret = camera_->configure(config_.get());
 	if (ret < 0) {
 		std::cout << "Failed to configure camera" << std::endl;
 		return ret;
 	}
 
-	const StreamConfiguration &cfg = config_[0];
+	const StreamConfiguration &cfg = config_->at(0);
 	Stream *stream = cfg.stream();
 	ret = viewfinder_->setFormat(cfg.pixelFormat, cfg.size.width,
 				     cfg.size.height);
@@ -180,6 +180,8 @@ void MainWindow::stopCapture()
 
 	camera_->freeBuffers();
 	isCapturing_ = false;
+
+	config_.reset();
 }
 
 void MainWindow::requestComplete(Request *request,

src/qcam/main_window.h

@@ -8,6 +8,7 @@
 #define __QCAM_MAIN_WINDOW_H__
 
 #include <map>
+#include <memory>
 
 #include <QMainWindow>
 
@@ -45,7 +46,7 @@ private:
 
 	std::shared_ptr<Camera> camera_;
 	bool isCapturing_;
-	CameraConfiguration config_;
+	std::unique_ptr<CameraConfiguration> config_;
 
 	ViewFinder *viewfinder_;
 };