d/ns,rs: Add external slam tracking type

src/xrt/drivers/north_star/ns_hmd.c

@@ -364,6 +364,10 @@ ns_hmd_create(const char *config_path, bool print_spew, bool print_debug)
 
 	ns->base.orientation_tracking_supported = true;
 	ns->base.position_tracking_supported = ns->tracker != NULL;
+	if (ns->tracker) {
+		ns->base.tracking_origin->type =
+		    ns->tracker->tracking_origin->type;
+	}
 	ns->base.device_type = XRT_DEVICE_TYPE_HMD;
 
 	return &ns->base;

src/xrt/drivers/realsense/rs_6dof.c

@@ -310,6 +310,8 @@ rs_6dof_create(void)
 	rs->base.name = XRT_DEVICE_GENERIC_HMD; // This is a lie.
 	rs->pose.orientation.w = 1.0f;          // All other values set to zero.
 
+	rs->base.tracking_origin->type = XRT_TRACKING_TYPE_EXTERNAL_SLAM;
+
 	// Print name.
 	snprintf(rs->base.str, XRT_DEVICE_NAME_LEN, "Intel RealSense 6-DOF");
 

src/xrt/include/xrt/xrt_tracking.h

@@ -50,7 +50,10 @@ enum xrt_tracking_type
 	XRT_TRACKING_TYPE_LIGHTHOUSE,
 
 	// The device(s) are tracked by Hydra
-	XRT_TRACKING_TYPE_HYDRA
+	XRT_TRACKING_TYPE_HYDRA,
+
+	// The device(s) are tracked by external SLAM
+	XRT_TRACKING_TYPE_EXTERNAL_SLAM,
 };
 
 /*!