10 files changed, 199 insertions, 184 deletions

diff --git a/src/cam/main.cpp b/src/cam/main.cpp
index d603228c..cd165bea 100644
--- a/src/cam/main.cpp
+++ b/src/cam/main.cpp
@@ -89,12 +89,9 @@ static int prepareCameraConfig(CameraConfiguration *config)
 {
 	StreamRoles roles;
 
-	streamInfo.clear();
-
 	/* If no configuration is provided assume a single video stream. */
 	if (!options.isSet(OptStream)) {
 		*config = camera->generateConfiguration({ StreamRole::VideoRecording });
-		streamInfo[config->front()] = "stream0";
 		return 0;
 	}
 
@@ -129,27 +126,20 @@ static int prepareCameraConfig(CameraConfiguration *config)
 	}
 
 	/* Apply configuration explicitly requested. */
-	CameraConfiguration::iterator it = config->begin();
+	unsigned int i = 0;
 	for (auto const &value : streamOptions) {
 		KeyValueParser::Options conf = value.toKeyValues();
-		Stream *stream = *it;
-		it++;
+		StreamConfiguration &cfg = (*config)[i++];
 
 		if (conf.isSet("width"))
-			(*config)[stream].size.width = conf["width"];
+			cfg.size.width = conf["width"];
 
 		if (conf.isSet("height"))
-			(*config)[stream].size.height = conf["height"];
+			cfg.size.height = conf["height"];
 
 		/* TODO: Translate 4CC string to ID. */
 		if (conf.isSet("pixelformat"))
-			(*config)[stream].pixelFormat = conf["pixelformat"];
-	}
-
-	unsigned int index = 0;
-	for (Stream *stream : *config) {
-		streamInfo[stream] = "stream" + std::to_string(index);
-		index++;
+			cfg.pixelFormat = conf["pixelformat"];
 	}
 
 	return 0;
@@ -216,6 +206,13 @@ static int capture()
 		return ret;
 	}
 
+	streamInfo.clear();
+
+	for (unsigned int index = 0; index < config.size(); ++index) {
+		StreamConfiguration &cfg = config[index];
+		streamInfo[cfg.stream()] = "stream" + std::to_string(index);
+	}
+
 	ret = camera->allocateBuffers();
 	if (ret) {
 		std::cerr << "Failed to allocate buffers"
@@ -227,8 +224,10 @@ static int capture()
 
 	/* Identify the stream with the least number of buffers. */
 	unsigned int nbuffers = UINT_MAX;
-	for (Stream *stream : config)
+	for (StreamConfiguration &cfg : config) {
+		Stream *stream = cfg.stream();
 		nbuffers = std::min(nbuffers, stream->bufferPool().count());
+	}
 
 	/*
 	 * TODO: make cam tool smarter to support still capture by for
@@ -245,8 +244,10 @@ static int capture()
 		}
 
 		std::map<Stream *, Buffer *> map;
-		for (Stream *stream : config)
+		for (StreamConfiguration &cfg : config) {
+			Stream *stream = cfg.stream();
 			map[stream] = &stream->bufferPool().buffers()[i];
+		}
 
 		ret = request->setBuffers(map);
 		if (ret < 0) {
diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
index a3921f91..5848330f 100644
--- a/src/libcamera/camera.cpp
+++ b/src/libcamera/camera.cpp
@@ -46,72 +46,40 @@ LOG_DECLARE_CATEGORY(Camera)
  * \class CameraConfiguration
  * \brief Hold configuration for streams of the camera
 
- * The CameraConfiguration holds an ordered list of streams and their associated
- * StreamConfiguration. From a data storage point of view, the class operates as
- * a map of Stream pointers to StreamConfiguration, with entries accessed with
- * operator[](Stream *). Accessing an entry for a Stream pointer not yet stored
- * in the configuration inserts a new empty entry.
- *
- * The class also suppors iterators, and from that point of view operates as a
- * vector of Stream pointers. The streams are iterated in insertion order, and
- * the operator[](int) returns the Stream pointer based on its insertion index.
- * Accessing a stream with an invalid index returns a null pointer.
+ * The CameraConfiguration holds an ordered list of stream configurations. It
+ * supports iterators and operates as a vector of StreamConfiguration instances.
+ * The stream configurations are inserted by addConfiguration(), and the
+ * operator[](int) returns a reference to the StreamConfiguration based on its
+ * insertion index. Accessing a stream configuration with an invalid index
+ * results in undefined behaviour.
  */
 
 /**
  * \typedef CameraConfiguration::iterator
- * \brief Iterator for the streams in the configuration
+ * \brief Iterator for the stream configurations in the camera configuration
  */
 
 /**
  * \typedef CameraConfiguration::const_iterator
- * \brief Const iterator for the streams in the configuration
+ * \brief Const iterator for the stream configuration in the camera
+ * configuration
  */
 
 /**
  * \brief Create an empty camera configuration
  */
 CameraConfiguration::CameraConfiguration()
-	: order_({}), config_({})
-{
-}
-
-/**
- * \brief Retrieve an iterator to the first stream in the sequence
- * \return An iterator to the first stream
- */
-std::vector<Stream *>::iterator CameraConfiguration::begin()
+	: config_({})
 {
-	return order_.begin();
 }
 
 /**
- * \brief Retrieve an iterator pointing to the past-the-end stream in the
- * sequence
- * \return An iterator to the element following the last stream
- */
-std::vector<Stream *>::iterator CameraConfiguration::end()
-{
-	return order_.end();
-}
-
-/**
- * \brief Retrieve a const iterator to the first element of the streams
- * \return A const iterator to the first stream
- */
-std::vector<Stream *>::const_iterator CameraConfiguration::begin() const
-{
-	return order_.begin();
-}
-
-/**
- * \brief Retrieve a const iterator pointing to the past-the-end stream in the
- * sequence
- * \return A const iterator to the element following the last stream
+ * \brief Add a stream configuration to the camera configuration
+ * \param[in] cfg The stream configuration
  */
-std::vector<Stream *>::const_iterator CameraConfiguration::end() const
+void CameraConfiguration::addConfiguration(const StreamConfiguration &cfg)
 {
-	return order_.end();
+	config_.push_back(cfg);
 }
 
 /**
@@ -125,12 +93,10 @@ std::vector<Stream *>::const_iterator CameraConfiguration::end() const
  */
 bool CameraConfiguration::isValid() const
 {
-	if (isEmpty())
+	if (empty())
 		return false;
 
-	for (auto const &it : config_) {
-		const StreamConfiguration &cfg = it.second;
-
+	for (const StreamConfiguration &cfg : config_) {
 		if (cfg.size.width == 0 || cfg.size.height == 0 ||
 		    cfg.pixelFormat == 0 || cfg.bufferCount == 0)
 			return false;
@@ -140,89 +106,116 @@ bool CameraConfiguration::isValid() const
 }
 
 /**
- * \brief Check if the camera configuration is empty
- * \return True if the configuration is empty
+ * \brief Retrieve a reference to a stream configuration
+ * \param[in] index Numerical index
+ *
+ * The \a index represents the zero based insertion order of stream
+ * configuration into the camera configuration with addConfiguration(). Calling
+ * this method with an invalid index results in undefined behaviour.
+ *
+ * \return The stream configuration
  */
-bool CameraConfiguration::isEmpty() const
+StreamConfiguration &CameraConfiguration::at(unsigned int index)
 {
-	return order_.empty();
+	return config_[index];
 }
 
 /**
- * \brief Retrieve the number of stream configurations
- * \return Number of stream configurations
+ * \brief Retrieve a const reference to a stream configuration
+ * \param[in] index Numerical index
+ *
+ * The \a index represents the zero based insertion order of stream
+ * configuration into the camera configuration with addConfiguration(). Calling
+ * this method with an invalid index results in undefined behaviour.
+ *
+ * \return The stream configuration
  */
-std::size_t CameraConfiguration::size() const
+const StreamConfiguration &CameraConfiguration::at(unsigned int index) const
 {
-	return order_.size();
+	return config_[index];
 }
 
 /**
- * \brief Access the first stream in the configuration
- * \return The first stream in the configuration
+ * \fn StreamConfiguration &CameraConfiguration::operator[](unsigned int)
+ * \brief Retrieve a reference to a stream configuration
+ * \param[in] index Numerical index
+ *
+ * The \a index represents the zero based insertion order of stream
+ * configuration into the camera configuration with addConfiguration(). Calling
+ * this method with an invalid index results in undefined behaviour.
+ *
+ * \return The stream configuration
+ */
+
+/**
+ * \fn const StreamConfiguration &CameraConfiguration::operator[](unsigned int) const
+ * \brief Retrieve a const reference to a stream configuration
+ * \param[in] index Numerical index
+ *
+ * The \a index represents the zero based insertion order of stream
+ * configuration into the camera configuration with addConfiguration(). Calling
+ * this method with an invalid index results in undefined behaviour.
+ *
+ * \return The stream configuration
+ */
+
+/**
+ * \brief Retrieve an iterator to the first stream configuration in the
+ * sequence
+ * \return An iterator to the first stream configuration
  */
-Stream *CameraConfiguration::front()
+CameraConfiguration::iterator CameraConfiguration::begin()
 {
-	return order_.front();
+	return config_.begin();
 }
 
 /**
- * \brief Access the first stream in the configuration
- * \return The first const stream pointer in the configuration
+ * \brief Retrieve a const iterator to the first element of the stream
+ * configurations
+ * \return A const iterator to the first stream configuration
  */
-const Stream *CameraConfiguration::front() const
+CameraConfiguration::const_iterator CameraConfiguration::begin() const
 {
-	return order_.front();
+	return config_.begin();
 }
 
 /**
- * \brief Retrieve a stream pointer from index
- * \param[in] index Numerical index
- *
- * The \a index represents the zero based insertion order of stream and stream
- * configuration into the camera configuration.
- *
- * \return The stream pointer at index, or a nullptr if the index is out of
- * bounds
+ * \brief Retrieve an iterator pointing to the past-the-end stream
+ * configuration in the sequence
+ * \return An iterator to the element following the last stream configuration
  */
-Stream *CameraConfiguration::operator[](unsigned int index) const
+CameraConfiguration::iterator CameraConfiguration::end()
 {
-	if (index >= order_.size())
-		return nullptr;
-
-	return order_.at(index);
+	return config_.end();
 }
 
 /**
- * \brief Retrieve a reference to a stream configuration
- * \param[in] stream Stream to retrieve configuration for
- *
- * If the camera configuration does not yet contain a configuration for
- * the requested stream, create and return an empty stream configuration.
- *
- * \return The configuration for the stream
+ * \brief Retrieve a const iterator pointing to the past-the-end stream
+ * configuration in the sequence
+ * \return A const iterator to the element following the last stream
+ * configuration
  */
-StreamConfiguration &CameraConfiguration::operator[](Stream *stream)
+CameraConfiguration::const_iterator CameraConfiguration::end() const
 {
-	if (config_.find(stream) == config_.end())
-		order_.push_back(stream);
+	return config_.end();
+}
 
-	return config_[stream];
+/**
+ * \brief Check if the camera configuration is empty
+ * \return True if the configuration is empty
+ */
+bool CameraConfiguration::empty() const
+{
+	return config_.empty();
 }
 
 /**
- * \brief Retrieve a const reference to a stream configuration
- * \param[in] stream Stream to retrieve configuration for
- *
- * No new stream configuration is created if called with \a stream that is not
- * already part of the camera configuration, doing so is an invalid operation
- * and results in undefined behaviour.
- *
- * \return The configuration for the stream
+ * \brief Retrieve the number of stream configurations
+ * \return Number of stream configurations
  */
-const StreamConfiguration &CameraConfiguration::operator[](Stream *stream) const
+std::size_t CameraConfiguration::size() const
 {
-	return config_.at(stream);
+	return config_.size();
 }
 
 /**
@@ -561,13 +554,9 @@ Camera::generateConfiguration(const StreamRoles &roles)
 	CameraConfiguration config = pipe_->generateConfiguration(this, roles);
 
 	std::ostringstream msg("streams configuration:", std::ios_base::ate);
-	unsigned int index = 0;
 
-	for (Stream *stream : config) {
-		const StreamConfiguration &cfg = config[stream];
-		msg << " (" << index << ") " << cfg.toString();
-		index++;
-	}
+	for (unsigned int index = 0; index < config.size(); ++index)
+		msg << " (" << index << ") " << config[index].toString();
 
 	LOG(Camera, Debug) << msg.str();
 
@@ -593,12 +582,15 @@ Camera::generateConfiguration(const StreamRoles &roles)
  *
  * This function affects the state of the camera, see \ref camera_operation.
  *
+ * Upon return the StreamConfiguration entries in \a config are associated with
+ * Stream instances which can be retrieved with StreamConfiguration::stream().
+ *
  * \return 0 on success or a negative error code otherwise
  * \retval -ENODEV The camera has been disconnected from the system
  * \retval -EACCES The camera is not in a state where it can be configured
  * \retval -EINVAL The configuration is not valid
  */
-int Camera::configure(const CameraConfiguration &config)
+int Camera::configure(CameraConfiguration &config)
 {
 	int ret;
 
@@ -615,16 +607,11 @@ int Camera::configure(const CameraConfiguration &config)
 	}
 
 	std::ostringstream msg("configuring streams:", std::ios_base::ate);
-	unsigned int index = 0;
 
-	for (Stream *stream : config) {
-		if (streams_.find(stream) == streams_.end())
-			return -EINVAL;
-
-		const StreamConfiguration &cfg = config[stream];
-		msg << std::dec << " (" << index << ") " << cfg.toString();
-
-		index++;
+	for (unsigned int index = 0; index < config.size(); ++index) {
+		StreamConfiguration &cfg = config[index];
+		cfg.setStream(nullptr);
+		msg << " (" << index << ") " << cfg.toString();
 	}
 
 	LOG(Camera, Info) << msg.str();
@@ -634,8 +621,11 @@ int Camera::configure(const CameraConfiguration &config)
 		return ret;
 
 	activeStreams_.clear();
-	for (Stream *stream : config) {
-		const StreamConfiguration &cfg = config[stream];
+	for (const StreamConfiguration &cfg : config) {
+		Stream *stream = cfg.stream();
+		if (!stream)
+			LOG(Camera, Fatal)
+				<< "Pipeline handler failed to update stream configuration";
 
 		stream->configuration_ = cfg;
 		activeStreams_.insert(stream);
diff --git a/src/libcamera/include/pipeline_handler.h b/src/libcamera/include/pipeline_handler.h
index 3352cb0e..a025905a 100644
--- a/src/libcamera/include/pipeline_handler.h
+++ b/src/libcamera/include/pipeline_handler.h
@@ -62,7 +62,7 @@ public:
 
 	virtual CameraConfiguration
 	generateConfiguration(Camera *camera, const StreamRoles &roles) = 0;
-	virtual int configure(Camera *camera, const CameraConfiguration &config) = 0;
+	virtual int configure(Camera *camera, CameraConfiguration &config) = 0;
 
 	virtual int allocateBuffers(Camera *camera,
 				    const std::set<Stream *> &streams) = 0;
diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
index d234a8ac..ed0ef69d 100644
--- a/src/libcamera/pipeline/ipu3/ipu3.cpp
+++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
@@ -152,8 +152,7 @@ public:
 
 	CameraConfiguration
 	generateConfiguration(Camera *camera, const StreamRoles &roles) override;
-	int configure(Camera *camera,
-		      const CameraConfiguration &config) override;
+	int configure(Camera *camera, CameraConfiguration &config) override;
 
 	int allocateBuffers(Camera *camera,
 			    const std::set<Stream *> &streams) override;
@@ -299,14 +298,13 @@ PipelineHandlerIPU3::generateConfiguration(Camera *camera,
 		cfg.pixelFormat = V4L2_PIX_FMT_NV12;
 		cfg.bufferCount = IPU3_BUFFER_COUNT;
 
-		config[stream] = cfg;
+		config.addConfiguration(cfg);
 	}
 
 	return config;
 }
 
-int PipelineHandlerIPU3::configure(Camera *camera,
-				   const CameraConfiguration &config)
+int PipelineHandlerIPU3::configure(Camera *camera, CameraConfiguration &config)
 {
 	IPU3CameraData *data = cameraData(camera);
 	IPU3Stream *outStream = &data->outStream_;
@@ -318,9 +316,13 @@ int PipelineHandlerIPU3::configure(Camera *camera,
 
 	outStream->active_ = false;
 	vfStream->active_ = false;
-	for (Stream *s : config) {
-		IPU3Stream *stream = static_cast<IPU3Stream *>(s);
-		const StreamConfiguration &cfg = config[stream];
+	for (StreamConfiguration &cfg : config) {
+		/*
+		 * Pick a stream for the configuration entry.
+		 * \todo: This is a naive temporary implementation that will be
+		 * reworked when implementing camera configuration validation.
+		 */
+		IPU3Stream *stream = vfStream->active_ ? outStream : vfStream;
 
 		/*
 		 * Verify that the requested size respects the IPU3 alignment
@@ -355,6 +357,7 @@ int PipelineHandlerIPU3::configure(Camera *camera,
 			sensorSize.height = cfg.size.height;
 
 		stream->active_ = true;
+		cfg.setStream(stream);
 	}
 
 	/*
@@ -379,10 +382,9 @@ int PipelineHandlerIPU3::configure(Camera *camera,
 		return ret;
 
 	/* Apply the format to the configured streams output devices. */
-	for (Stream *s : config) {
-		IPU3Stream *stream = static_cast<IPU3Stream *>(s);
-
-		ret = imgu->configureOutput(stream->device_, config[stream]);
+	for (StreamConfiguration &cfg : config) {
+		IPU3Stream *stream = static_cast<IPU3Stream *>(cfg.stream());
+		ret = imgu->configureOutput(stream->device_, cfg);
 		if (ret)
 			return ret;
 	}
@@ -393,15 +395,13 @@ int PipelineHandlerIPU3::configure(Camera *camera,
 	 * be at least one active stream in the configuration request).
 	 */
 	if (!outStream->active_) {
-		ret = imgu->configureOutput(outStream->device_,
-					    config[vfStream]);
+		ret = imgu->configureOutput(outStream->device_, config[0]);
 		if (ret)
 			return ret;
 	}
 
 	if (!vfStream->active_) {
-		ret = imgu->configureOutput(vfStream->device_,
-					    config[outStream]);
+		ret = imgu->configureOutput(vfStream->device_, config[0]);
 		if (ret)
 			return ret;
 	}
diff --git a/src/libcamera/pipeline/rkisp1/rkisp1.cpp b/src/libcamera/pipeline/rkisp1/rkisp1.cpp
index 4bd8c510..ec6980b0 100644
--- a/src/libcamera/pipeline/rkisp1/rkisp1.cpp
+++ b/src/libcamera/pipeline/rkisp1/rkisp1.cpp
@@ -36,8 +36,7 @@ public:
 
 	CameraConfiguration generateConfiguration(Camera *camera,
 		const StreamRoles &roles) override;
-	int configure(Camera *camera,
-		const CameraConfiguration &config) override;
+	int configure(Camera *camera, CameraConfiguration &config) override;
 
 	int allocateBuffers(Camera *camera,
 		const std::set<Stream *> &streams) override;
@@ -117,16 +116,15 @@ CameraConfiguration PipelineHandlerRkISP1::generateConfiguration(Camera *camera,
 	cfg.size = data->sensor_->resolution();
 	cfg.bufferCount = RKISP1_BUFFER_COUNT;
 
-	config[&data->stream_] = cfg;
+	config.addConfiguration(cfg);
 
 	return config;
 }
 
-int PipelineHandlerRkISP1::configure(Camera *camera,
-				     const CameraConfiguration &config)
+int PipelineHandlerRkISP1::configure(Camera *camera, CameraConfiguration &config)
 {
 	RkISP1CameraData *data = cameraData(camera);
-	const StreamConfiguration &cfg = config[&data->stream_];
+	StreamConfiguration &cfg = config[0];
 	CameraSensor *sensor = data->sensor_;
 	int ret;
 
@@ -217,6 +215,8 @@ int PipelineHandlerRkISP1::configure(Camera *camera,
 		return -EINVAL;
 	}
 
+	cfg.setStream(&data->stream_);
+
 	return 0;
 }
 
diff --git a/src/libcamera/pipeline/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo.cpp
index d2e1f7d4..5dcc868b 100644
--- a/src/libcamera/pipeline/uvcvideo.cpp
+++ b/src/libcamera/pipeline/uvcvideo.cpp
@@ -27,8 +27,7 @@ public:
 
 	CameraConfiguration
 	generateConfiguration(Camera *camera, const StreamRoles &roles) override;
-	int configure(Camera *camera,
-		      const CameraConfiguration &config) override;
+	int configure(Camera *camera, CameraConfiguration &config) override;
 
 	int allocateBuffers(Camera *camera,
 			    const std::set<Stream *> &streams) override;
@@ -78,38 +77,38 @@ CameraConfiguration
 PipelineHandlerUVC::generateConfiguration(Camera *camera,
 					  const StreamRoles &roles)
 {
-	UVCCameraData *data = cameraData(camera);
 	CameraConfiguration config;
-	StreamConfiguration cfg{};
+	StreamConfiguration cfg;
 
 	cfg.pixelFormat = V4L2_PIX_FMT_YUYV;
 	cfg.size = { 640, 480 };
 	cfg.bufferCount = 4;
 
-	config[&data->stream_] = cfg;
+	config.addConfiguration(cfg);
 
 	return config;
 }
 
-int PipelineHandlerUVC::configure(Camera *camera,
-				  const CameraConfiguration &config)
+int PipelineHandlerUVC::configure(Camera *camera, CameraConfiguration &config)
 {
 	UVCCameraData *data = cameraData(camera);
-	const StreamConfiguration *cfg = &config[&data->stream_];
+	StreamConfiguration &cfg = config[0];
 	int ret;
 
 	V4L2DeviceFormat format = {};
-	format.fourcc = cfg->pixelFormat;
-	format.size = cfg->size;
+	format.fourcc = cfg.pixelFormat;
+	format.size = cfg.size;
 
 	ret = data->video_->setFormat(&format);
 	if (ret)
 		return ret;
 
-	if (format.size != cfg->size ||
-	    format.fourcc != cfg->pixelFormat)
+	if (format.size != cfg.size ||
+	    format.fourcc != cfg.pixelFormat)
 		return -EINVAL;
 
+	cfg.setStream(&data->stream_);
+
 	return 0;
 }
 
diff --git a/src/libcamera/pipeline/vimc.cpp b/src/libcamera/pipeline/vimc.cpp
index 17e2491e..af6b6f21 100644
--- a/src/libcamera/pipeline/vimc.cpp
+++ b/src/libcamera/pipeline/vimc.cpp
@@ -27,8 +27,7 @@ public:
 
 	CameraConfiguration
 	generateConfiguration(Camera *camera, const StreamRoles &roles) override;
-	int configure(Camera *camera,
-		      const CameraConfiguration &config) override;
+	int configure(Camera *camera, CameraConfiguration &config) override;
 
 	int allocateBuffers(Camera *camera,
 			    const std::set<Stream *> &streams) override;
@@ -78,38 +77,38 @@ CameraConfiguration
 PipelineHandlerVimc::generateConfiguration(Camera *camera,
 					   const StreamRoles &roles)
 {
-	VimcCameraData *data = cameraData(camera);
 	CameraConfiguration config;
-	StreamConfiguration cfg{};
+	StreamConfiguration cfg;
 
 	cfg.pixelFormat = V4L2_PIX_FMT_RGB24;
 	cfg.size = { 640, 480 };
 	cfg.bufferCount = 4;
 
-	config[&data->stream_] = cfg;
+	config.addConfiguration(cfg);
 
 	return config;
 }
 
-int PipelineHandlerVimc::configure(Camera *camera,
-				   const CameraConfiguration &config)
+int PipelineHandlerVimc::configure(Camera *camera, CameraConfiguration &config)
 {
 	VimcCameraData *data = cameraData(camera);
-	const StreamConfiguration *cfg = &config[&data->stream_];
+	StreamConfiguration &cfg = config[0];
 	int ret;
 
 	V4L2DeviceFormat format = {};
-	format.fourcc = cfg->pixelFormat;
-	format.size = cfg->size;
+	format.fourcc = cfg.pixelFormat;
+	format.size = cfg.size;
 
 	ret = data->video_->setFormat(&format);
 	if (ret)
 		return ret;
 
-	if (format.size != cfg->size ||
-	    format.fourcc != cfg->pixelFormat)
+	if (format.size != cfg.size ||
+	    format.fourcc != cfg.pixelFormat)
 		return -EINVAL;
 
+	cfg.setStream(&data->stream_);
+
 	return 0;
 }
 
diff --git a/src/libcamera/pipeline_handler.cpp b/src/libcamera/pipeline_handler.cpp
index 81c11149..4185e355 100644
--- a/src/libcamera/pipeline_handler.cpp
+++ b/src/libcamera/pipeline_handler.cpp
@@ -255,6 +255,10 @@ void PipelineHandler::unlock()
  * configuration of a subset of the streams can't be satisfied, the
  * whole configuration is considered invalid.
  *
+ * Once the configuration is validated and the camera configured, the pipeline
+ * handler shall associate a Stream instance to each StreamConfiguration entry
+ * in the CameraConfiguration with the StreamConfiguration::setStream() method.
+ *
  * \return 0 on success or a negative error code otherwise
  */
 
diff --git a/src/libcamera/stream.cpp b/src/libcamera/stream.cpp
index fe4c4ecf..0c59a31a 100644
--- a/src/libcamera/stream.cpp
+++ b/src/libcamera/stream.cpp
@@ -59,6 +59,28 @@ namespace libcamera {
  */
 
 /**
+ * \fn StreamConfiguration::stream()
+ * \brief Retrieve the stream associated with the configuration
+ *
+ * When a camera is configured with Camera::configure() Stream instances are
+ * associated with each stream configuration entry. This method retrieves the
+ * associated Stream, which remains valid until the next call to
+ * Camera::configure() or Camera::release().
+ *
+ * \return The stream associated with the configuration
+ */
+
+/**
+ * \fn StreamConfiguration::setStream()
+ * \brief Associate a stream with a configuration
+ *
+ * This method is meant for the PipelineHandler::configure() method and shall
+ * not be called by applications.
+ *
+ * \param[in] stream The stream
+ */
+
+/**
  * \brief Assemble and return a string describing the configuration
  *
  * \return A string describing the StreamConfiguration
diff --git a/src/qcam/main_window.cpp b/src/qcam/main_window.cpp
index a984aaca..06ae2985 100644
--- a/src/qcam/main_window.cpp
+++ b/src/qcam/main_window.cpp
@@ -98,14 +98,14 @@ int MainWindow::startCapture()
 	int ret;
 
 	config_ = camera_->generateConfiguration({ StreamRole::VideoRecording });
-	Stream *stream = config_.front();
 	ret = camera_->configure(config_);
 	if (ret < 0) {
 		std::cout << "Failed to configure camera" << std::endl;
 		return ret;
 	}
 
-	const StreamConfiguration &cfg = config_[stream];
+	const StreamConfiguration &cfg = config_[0];
+	Stream *stream = cfg.stream();
 	ret = viewfinder_->setFormat(cfg.pixelFormat, cfg.size.width,
 				     cfg.size.height);
 	if (ret < 0) {