Unable to use onboard camer and usb camera

I want to use opencv to perform a face detection task.

I have installed jetpack4.4 gstreamer, and compile opencv3.4.6 by myself (I am sure that I have enabled gstreamer whem compiling). But when I try to open the camera with gstreamer:

when I connect a usb camera to my jetson tx2, ls dev/video* shows that:
/dev/video0
I think there’s something wrong because there should be two cameras like video0, video1
Furthermore v4l2-ctl --list-devices shows that:
USB2.0 Camera (usb-3530000.xhci-2.3):
/dev/video0

It seems that only the usb camera is detected

when I run:
gst-launch-1.0 nvarguscamerasrc ! ‘video/x-raw(memory:NVMM),
width=(int)1920, height=(int)1080, format=(string)NV12,
framerate=(fraction)30/1’ ! nvoverlaysink -e

it shows that:
Setting pipeline to PAUSED …
Pipeline is live and does not need PREROLL …
Setting pipeline to PLAYING …
New clock: GstSystemClock
Error generated. /dvs/git/dirty/git-master_linux/multimedia/nvgstreamer/gst-nvarguscamera/gstnvarguscamerasrc.cpp, execute:645 No cameras available

(gst-launch-1.0:8432): GStreamer-CRITICAL **: 21:36:07.397: gst_mini_object_set_qdata: assertion ‘object != NULL’ failed
Got EOS from element “pipeline0”.
Execution ended after 0:00:00.151404837
Setting pipeline to PAUSED …
Setting pipeline to READY …
Setting pipeline to NULL …
Freeing pipeline …

I am confused and when I try to use cheese to find out whether there is any camera working, it shows out that:

cheese

(cheese:8618): Gtk-WARNING **: 21:40:01.642: Theme parsing error: cheese.css:7:35: The style property GtkScrollbar:min-slider-length is deprecated and shouldn’t be used anymore. It will be removed in a future version
Opening in BLOCKING MODE
Segmentation fault (core dumped)

what should I do now to find out where is the problem?

From the v4l2-ctl --list-devices your system have USB camera only there’s no any CSI camera to run the nvarguscamerasrc.