libcamera: pipeline: uvcvideo: Generate unique camera names

Generate camera names that are unique and persistent between system
resets. The name is constructed from the USB device information as well
as the USB controller on the host.

Before this change example of camera names:

Venus USB2.0 Camera: Venus USB2
Logitech Webcam C930e

After this change the same cameras are:

\_SB_.PCI0.RP05.PXSX-2.1.1:1.0-0ac8:3420
\_SB_.PCI0.RP05.PXSX-2.4:1.0-046d:0843

On OF-based system:

/base/soc/usb@7e980000/usb-port@1-1.2:1.0-0ac8:3420

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

src/libcamera/pipeline/uvcvideo/uvcvideo.cpp

@@ -6,6 +6,7 @@
  */
 
 #include <algorithm>
+#include <fstream>
 #include <iomanip>
 #include <math.h>
 #include <tuple>
@@ -20,6 +21,7 @@
 #include "libcamera/internal/log.h"
 #include "libcamera/internal/media_device.h"
 #include "libcamera/internal/pipeline_handler.h"
+#include "libcamera/internal/sysfs.h"
 #include "libcamera/internal/utils.h"
 #include "libcamera/internal/v4l2_controls.h"
 #include "libcamera/internal/v4l2_videodevice.h"
@@ -81,6 +83,8 @@ public:
 	bool match(DeviceEnumerator *enumerator) override;
 
 private:
+	std::string generateId(const UVCCameraData *data);
+
 	int processControl(ControlList *controls, unsigned int id,
 			   const ControlValue &value);
 	int processControls(UVCCameraData *data, Request *request);
@@ -379,6 +383,69 @@ int PipelineHandlerUVC::queueRequestDevice(Camera *camera, Request *request)
 	return 0;
 }
 
+std::string PipelineHandlerUVC::generateId(const UVCCameraData *data)
+{
+	const std::string path = data->video_->devicePath();
+
+	/* Create a controller ID from first device described in firmware. */
+	std::string controllerId;
+	std::string searchPath = path;
+	while (true) {
+		std::string::size_type pos = searchPath.rfind('/');
+		if (pos <= 1) {
+			LOG(UVC, Error) << "Can not find controller ID";
+			return {};
+		}
+
+		searchPath = searchPath.substr(0, pos);
+
+		controllerId = sysfs::firmwareNodePath(searchPath);
+		if (!controllerId.empty())
+			break;
+	}
+
+	/*
+	 * Create a USB ID from the device path which has the known format:
+	 *
+	 *	path = bus, "-", ports, ":", config, ".", interface ;
+	 *	bus = number ;
+	 *	ports = port, [ ".", ports ] ;
+	 *	port = number ;
+	 *	config = number ;
+	 *	interface = number ;
+	 *
+	 * Example: 3-2.4:1.0
+	 *
+	 * The bus is not guaranteed to be stable and needs to be stripped from
+	 * the USB ID. The final USB ID is built up of the ports, config and
+	 * interface properties.
+	 *
+	 * Example 2.4:1.0.
+	 */
+	std::string usbId = utils::basename(path.c_str());
+	usbId = usbId.substr(usbId.find('-') + 1);
+
+	/* Creata a device ID from the USB devices vendor and product ID. */
+	std::string deviceId;
+	for (const std::string &name : { "idVendor", "idProduct" }) {
+		std::ifstream file(path + "/../" + name);
+
+		if (!file.is_open())
+			return {};
+
+		std::string value;
+		std::getline(file, value);
+		file.close();
+
+		if (!deviceId.empty())
+			deviceId += ":";
+
+		deviceId += value;
+	}
+
+	return controllerId + "-" + usbId + "-" + deviceId;
+}
+
 bool PipelineHandlerUVC::match(DeviceEnumerator *enumerator)
 {
 	MediaDevice *media;
@@ -405,8 +472,14 @@ bool PipelineHandlerUVC::match(DeviceEnumerator *enumerator)
 		return false;
 
 	/* Create and register the camera. */
+	std::string id = generateId(data.get());
+	if (id.empty()) {
+		LOG(UVC, Error) << "Failed to generate camera ID";
+		return false;
+	}
+
 	std::set<Stream *> streams{ &data->stream_ };
-	std::shared_ptr<Camera> camera = Camera::create(this, media->model(), streams);
+	std::shared_ptr<Camera> camera = Camera::create(this, id, streams);
 	registerCamera(std::move(camera), std::move(data));
 
 	/* Enable hot-unplug notifications. */