libcamera: stream: Shorten access to the bufferPool

All interactions with the Stream's buffers currently go through the
BufferPool. In order to shorten accessing the buffers array, and eventually
restrict access to the Stream's internal buffer pool, provide operations to
access, create and destroy buffers.

It is still possible to access the pool for pipeline handlers to
populate it by exporting buffers from a video device to Stream's pool.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

include/libcamera/stream.h

@@ -71,11 +71,15 @@ public:
 	std::unique_ptr<Buffer> createBuffer(unsigned int index);
 
 	BufferPool &bufferPool() { return bufferPool_; }
+	std::vector<BufferMemory> &buffers() { return bufferPool_.buffers(); }
 	const StreamConfiguration &configuration() const { return configuration_; }
 
 protected:
 	friend class Camera;
 
+	void createBuffers(unsigned int count);
+	void destroyBuffers();
+
 	BufferPool bufferPool_;
 	StreamConfiguration configuration_;
 };

src/cam/capture.cpp

@@ -154,7 +154,7 @@ void Capture::requestComplete(Request *request, const std::map<Stream *, Buffer
 	for (auto it = buffers.begin(); it != buffers.end(); ++it) {
 		Stream *stream = it->first;
 		Buffer *buffer = it->second;
-		BufferMemory *mem = &stream->bufferPool().buffers()[buffer->index()];
+		BufferMemory *mem = &stream->buffers()[buffer->index()];
 		const std::string &name = streamName_[stream];
 
 		info << " " << name

src/libcamera/camera.cpp

@@ -683,7 +683,7 @@ int Camera::configure(CameraConfiguration *config)
 		 * Allocate buffer objects in the pool.
 		 * Memory will be allocated and assigned later.
 		 */
-		stream->bufferPool().createBuffers(cfg.bufferCount);
+		stream->createBuffers(cfg.bufferCount);
 	}
 
 	state_ = CameraConfigured;
@@ -744,7 +744,7 @@ int Camera::freeBuffers()
 		 * All mappings must be destroyed before buffers can be freed
 		 * by the V4L2 device that has allocated them.
 		 */
-		stream->bufferPool().destroyBuffers();
+		stream->destroyBuffers();
 	}
 
 	state_ = CameraConfigured;

src/libcamera/stream.cpp

@@ -435,19 +435,51 @@ std::unique_ptr<Buffer> Stream::createBuffer(unsigned int index)
  * \fn Stream::bufferPool()
  * \brief Retrieve the buffer pool for the stream
  *
- * The buffer pool handles the buffers used to capture frames at the output of
- * the stream. It is initially created empty and shall be populated with
+ * The buffer pool handles the memory buffers used to store frames for the
+ * stream. It is initially created empty and shall be populated with
  * buffers before being used.
  *
  * \return A reference to the buffer pool
  */
 
+/**
+ * \fn Stream::buffers()
+ * \brief Retrieve the memory buffers in the Stream's buffer pool
+ * \return The list of stream's memory buffers
+ */
+
 /**
  * \fn Stream::configuration()
  * \brief Retrieve the active configuration of the stream
  * \return The active configuration of the stream
  */
 
+/**
+ * \brief Create buffers for the stream
+ * \param[in] count The number of buffers to create
+ *
+ * Create \a count empty buffers in the Stream's buffer pool.
+ */
+void Stream::createBuffers(unsigned int count)
+{
+	destroyBuffers();
+	if (count == 0)
+		return;
+
+	bufferPool_.createBuffers(count);
+}
+
+/**
+ * \brief Destroy buffers in the stream
+ *
+ * If no buffers have been created or if buffers have already been destroyed no
+ * operation is performed.
+ */
+void Stream::destroyBuffers()
+{
+	bufferPool_.destroyBuffers();
+}
+
 /**
  * \var Stream::bufferPool_
  * \brief The pool of buffers associated with the stream

src/qcam/main_window.cpp

@@ -235,7 +235,7 @@ void MainWindow::requestComplete(Request *request,
 		  << " fps: " << std::fixed << std::setprecision(2) << fps
 		  << std::endl;
 
-	BufferMemory *mem = &stream->bufferPool().buffers()[buffer->index()];
+	BufferMemory *mem = &stream->buffers()[buffer->index()];
 	display(buffer, mem);
 
 	request = camera_->createRequest();