I bought a TX2 developer Kit and connected it to a regular LCD Display through HDMI cable. The board was flashed with version 28.2.1 via JetPack.
I found that I cannot control the screen brightness in the Ubuntu System Settings, and I cannot change the brightness from command line either. I notice that this folder /sys/class/backlight/ is empty.
My goal is to control brightness using software. Is it possible to do that just through the HDMI cable? Or what else should I do? Any pointer would be helpful to me.