[libcamera-devel] [RFC PATCH v2 1/5] libcamera: pipeline: uvcvideo: Add UVC metadata node

[Gabby George]

Identify and open the UVC metadata's video node. This will give us
access to metadata associated with the video stream of the uvc camera.
The user will not have access to this video node and will not need to
manage its data in any way.

Signed-off-by: Gabby George <gabbymg94 at gmail.com>
---
 src/libcamera/pipeline/uvcvideo/uvcvideo.cpp | 42 ++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
index 38f48a5d..dbe0cc8c 100644
--- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
+++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
@@ -49,10 +49,13 @@ public:
 	const std::string &id() const { return id_; }
 
 	std::unique_ptr<V4L2VideoDevice> video_;
+	std::unique_ptr<V4L2VideoDevice> metadata_;
 	Stream stream_;
 	std::map<PixelFormat, std::vector<SizeRange>> formats_;
 
 private:
+	int initMetadata(MediaDevice *media);
+
 	bool generateId();
 
 	std::string id_;
@@ -411,6 +414,39 @@ bool PipelineHandlerUVC::match(DeviceEnumerator *enumerator)
 	return true;
 }
 
+int UVCCameraData::initMetadata(MediaDevice *media)
+{
+	int ret;
+
+	const std::vector<MediaEntity *> &entities = media->entities();
+	std::string dev_node_name = video_->deviceNode();
+	auto metadata = std::find_if(entities.begin(), entities.end(),
+				     [&dev_node_name](MediaEntity *e) {
+					     return e->type() == MediaEntity::Type::V4L2VideoDevice
+							&& !(e->flags() & MEDIA_ENT_FL_DEFAULT);
+				     });
+
+	if (metadata == entities.end()) {
+		return -ENODEV;
+	}
+
+	/* configure the metadata node */
+	metadata_ = std::make_unique<V4L2VideoDevice>(*metadata);
+	ret = metadata_->open();
+	if (ret)
+		return ret;
+
+	if (!(metadata_->caps().isMeta())) {
+		/*
+		 * UVC Devices are usually only anticipated to expose two
+         * devices, so we assume the non-default device is the metadata
+         * device node
+		 */
+		return -EINVAL;
+	}
+	return 0;
+}
+
 int UVCCameraData::init(MediaDevice *media)
 {
 	int ret;
@@ -512,6 +548,12 @@ int UVCCameraData::init(MediaDevice *media)
 
 	controlInfo_ = ControlInfoMap(std::move(ctrls), controls::controls);
 
+	ret = initMetadata(media);
+	if (ret) {
+		metadata_ = nullptr;
+		LOG(UVC, Error) << "Could not find a metadata video device.";
+	}
+
 	return 0;
 }
 
-- 
2.34.1