v4l2_scan_controls  685 modules/videoio/src/cap_libv4l.cpp    v4l2_scan_controls(capture);
v4l2_scan_controls 1621 modules/videoio/src/cap_libv4l.cpp     v4l2_scan_controls(capture);
v4l2_scan_controls  833 modules/videoio/src/cap_v4l.cpp    v4l2_scan_controls(capture);