--get-video-device => ???

[CarlFK]

note: I am assuming this should work given the syslog:
[21775.690321] uvcvideo: Found UVC 1.00 device HDMI2USB.tv - Numato Opsis Board (2a19:5442)
this is from my damaged Opsis and the testing firmware that may not work.
I was not able to get a console or stream, but I also didn't try very hard.

juser@cnt6:~/HDMI2USB-firmware-prebuilt/opsis/firmware/testing$ hdmi2usb-mode-switch --get-video-device
???

juser@cnt6:~/HDMI2USB-firmware-prebuilt/opsis/firmware/testing$ hdmi2usb-mode-switch --get-serial-device
/dev/ttyACM0

dmesg
[21775.415615] usb 4-1.3: new high-speed USB device number 14 using ehci-pci
[21775.523991] usb 4-1.3: config 1 interface 2 altsetting 0 endpoint 0x81 has an invalid bInterval 64, changing to 10
[21775.524472] usb 4-1.3: New USB device found, idVendor=2a19, idProduct=5442
[21775.524473] usb 4-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[21775.524474] usb 4-1.3: Product: HDMI2USB.tv - Numato Opsis Board
[21775.524475] usb 4-1.3: Manufacturer: TimVideos.us
[21775.524476] usb 4-1.3: SerialNumber: 0000000000000000
[21775.684082] media: Linux media interface: v0.10
[21775.687153] Linux video capture interface: v2.00
[21775.690321] uvcvideo: Found UVC 1.00 device HDMI2USB.tv - Numato Opsis Board (2a19:5442)
[21775.690606] uvcvideo: UVC non compliance - GET_DEF(PROBE) not supported. Enabling workaround.
[21775.691188] uvcvideo 4-1.3:1.0: Entity type for entity Extension 3 was not initialized!
[21775.691190] uvcvideo 4-1.3:1.0: Entity type for entity Processing 2 was not initialized!
[21775.691191] uvcvideo 4-1.3:1.0: Entity type for entity Camera 1 was not initialized!
[21775.691262] usbcore: registered new interface driver uvcvideo
[21775.691263] USB Video Class driver (1.1.1)
[21775.691826] cdc_acm 4-1.3:1.2: ttyACM0: USB ACM device
[21775.692238] usbcore: registered new interface driver cdc_acm
[21775.692238] cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters