This program will watchout for the buttom combo MIDDLE + RIGHT.
When triggered, it'll grab/ungrab the touchscreen evdev which will prevent any input to be processed by any other app other than the c program (like xochitl).
Compile it with gcc either on device or with the oecore (or older poky) cross compiler. No special settings should be required.
- Copy the binary to /home/root/touch_toggler