HI

I understand!

The device I tried to support was a USB Skype@phone EX-B
so I attempted to write a libusb uinput driver which I'm attaching
here for reference. I got up to working keypad, LED and ringer
without LCD or keypad and LCD without LED and ringer due to
EV_FF issue.

but now I got rid of this EX-B and obtained Yealink P1K that
already has driver in kernel, keyboard led ringer and display
all supported out of the box

If you can take some time, it would be maybe most useful to
look about what makes LED and SND being disabled by
EV_FF (no matter CUSTOM, SINE or any other type of effect)

Best regards, Davor