libcamera: pipeline_handler: Decouple buffer import and export

Use the V4L2 buffer orphaning feature, exposed through
V4L2VideoDevice::exportBuffers(), to decouple buffer import and export.
The PipelineHandler::importFrameBuffers() function is now called for all
streams regardless of whether exportFrameBuffers() has been called or
not. This simplifies the Camera implementation slightly, and opens the
door to additional simplifications.

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

include/libcamera/camera.h

@@ -113,7 +113,6 @@ private:
 	friend class FrameBufferAllocator;
 	int exportFrameBuffers(Stream *stream,
 			       std::vector<std::unique_ptr<FrameBuffer>> *buffers);
-	int freeFrameBuffers(Stream *stream);
 	/* \todo Remove allocator_ from the exposed API */
 	FrameBufferAllocator *allocator_;
 };

src/libcamera/camera.cpp

@@ -554,18 +554,6 @@ int Camera::exportFrameBuffers(Stream *stream,
 				       buffers);
 }
 
-int Camera::freeFrameBuffers(Stream *stream)
-{
-	int ret = p_->isAccessAllowed(Private::CameraConfigured, true);
-	if (ret < 0)
-		return ret;
-
-	p_->pipe_->invokeMethod(&PipelineHandler::freeFrameBuffers,
-				ConnectionTypeBlocking, this, stream);
-
-	return 0;
-}
-
 /**
  * \brief Acquire the camera device for exclusive access
  *
@@ -928,9 +916,6 @@ int Camera::start()
 	LOG(Camera, Debug) << "Starting capture";
 
 	for (Stream *stream : p_->activeStreams_) {
-		if (allocator_ && !allocator_->buffers(stream).empty())
-			continue;
-
 		ret = p_->pipe_->invokeMethod(&PipelineHandler::importFrameBuffers,
 					      ConnectionTypeDirect, this, stream);
 		if (ret < 0)
@@ -974,13 +959,9 @@ int Camera::stop()
 	p_->pipe_->invokeMethod(&PipelineHandler::stop, ConnectionTypeBlocking,
 				this);
 
-	for (Stream *stream : p_->activeStreams_) {
-		if (allocator_ && !allocator_->buffers(stream).empty())
-			continue;
-
+	for (Stream *stream : p_->activeStreams_)
 		p_->pipe_->invokeMethod(&PipelineHandler::freeFrameBuffers,
 					ConnectionTypeBlocking, this, stream);
-	}
 
 	return 0;
 }

src/libcamera/framebuffer_allocator.cpp

@@ -87,11 +87,6 @@ FrameBufferAllocator::FrameBufferAllocator(std::shared_ptr<Camera> camera)
 
 FrameBufferAllocator::~FrameBufferAllocator()
 {
-	for (auto &value : buffers_) {
-		Stream *stream = value.first;
-		camera_->freeFrameBuffers(stream);
-	}
-
 	buffers_.clear();
 
 	camera_->allocator_ = nullptr;
@@ -148,10 +143,6 @@ int FrameBufferAllocator::free(Stream *stream)
 	if (iter == buffers_.end())
 		return -EINVAL;
 
-	int ret = camera_->freeFrameBuffers(stream);
-	if (ret < 0)
-		return ret;
-
 	std::vector<std::unique_ptr<FrameBuffer>> &buffers = iter->second;
 	buffers.clear();
 	buffers_.erase(iter);

src/libcamera/pipeline/ipu3/ipu3.cpp

@@ -621,7 +621,7 @@ int PipelineHandlerIPU3::exportFrameBuffers(Camera *camera, Stream *stream,
 	V4L2VideoDevice *video = ipu3stream->device_->dev;
 	unsigned int count = stream->configuration().bufferCount;
 
-	return video->allocateBuffers(count, buffers);
+	return video->exportBuffers(count, buffers);
 }
 
 int PipelineHandlerIPU3::importFrameBuffers(Camera *camera, Stream *stream)

src/libcamera/pipeline/rkisp1/rkisp1.cpp

@@ -664,7 +664,7 @@ int PipelineHandlerRkISP1::exportFrameBuffers(Camera *camera, Stream *stream,
 					      std::vector<std::unique_ptr<FrameBuffer>> *buffers)
 {
 	unsigned int count = stream->configuration().bufferCount;
-	return video_->allocateBuffers(count, buffers);
+	return video_->exportBuffers(count, buffers);
 }
 
 int PipelineHandlerRkISP1::importFrameBuffers(Camera *camera, Stream *stream)

src/libcamera/pipeline/uvcvideo.cpp

@@ -211,7 +211,7 @@ int PipelineHandlerUVC::exportFrameBuffers(Camera *camera, Stream *stream,
 	UVCCameraData *data = cameraData(camera);
 	unsigned int count = stream->configuration().bufferCount;
 
-	return data->video_->allocateBuffers(count, buffers);
+	return data->video_->exportBuffers(count, buffers);
 }
 
 int PipelineHandlerUVC::importFrameBuffers(Camera *camera, Stream *stream)

src/libcamera/pipeline/vimc.cpp

@@ -264,7 +264,7 @@ int PipelineHandlerVimc::exportFrameBuffers(Camera *camera, Stream *stream,
 	VimcCameraData *data = cameraData(camera);
 	unsigned int count = stream->configuration().bufferCount;
 
-	return data->video_->allocateBuffers(count, buffers);
+	return data->video_->exportBuffers(count, buffers);
 }
 
 int PipelineHandlerVimc::importFrameBuffers(Camera *camera, Stream *stream)

src/libcamera/pipeline_handler.cpp

@@ -337,16 +337,7 @@ const ControlList &PipelineHandler::properties(Camera *camera)
  *
  * The method may only be called after the Camera has been configured and before
  * it gets started, or after it gets stopped. It shall be called only for
- * streams that are part of the active camera configuration, and at most once
- * per stream until buffers for the stream are freed with freeFrameBuffers().
- *
- * exportFrameBuffers() shall also allocate all other resources required by
- * the pipeline handler for the stream to prepare for starting the Camera. This
- * responsibility is shared with importFrameBuffers(), and one and only one of
- * those two methods shall be called for each stream until the buffers are
- * freed. The pipeline handler shall support all combinations of
- * exportFrameBuffers() and importFrameBuffers() for the streams contained in
- * any camera configuration.
+ * streams that are part of the active camera configuration.
  *
  * The only intended caller is Camera::exportFrameBuffers().
  *
@@ -371,12 +362,7 @@ const ControlList &PipelineHandler::properties(Camera *camera)
  * per stream until buffers for the stream are freed with freeFrameBuffers().
  *
  * importFrameBuffers() shall also allocate all other resources required by the
- * pipeline handler for the stream to prepare for starting the Camera. This
- * responsibility is shared with exportFrameBuffers(), and one and only one of
- * those two methods shall be called for each stream until the buffers are
- * freed. The pipeline handler shall support all combinations of
- * exportFrameBuffers() and importFrameBuffers() for the streams contained in
- * any camera configuration.
+ * pipeline handler for the stream to prepare for starting the Camera.
  *
  * The only intended caller is Camera::start().
  *
@@ -391,10 +377,9 @@ const ControlList &PipelineHandler::properties(Camera *camera)
  * \param[in] camera The camera
  * \param[in] stream The stream to free buffers for
  *
- * This method shall free all buffers and all other resources allocated for the
- * \a stream by exportFrameBuffers() or importFrameBuffers(). It shall be
- * called only after a successful call to either of these two methods, and only
- * once per stream.
+ * This method shall release all resources allocated for the \a stream by
+ * importFrameBuffers(). It shall be called only after a successful call that
+ * method, and only once per stream.
  *
  * The only intended callers are Camera::stop() and Camera::freeFrameBuffers().
  *