official RPF touchscreen not fully recognized?

Greetings,

I have a raspberry pi 3 with the official RPF 7" touchscreen.

When I boot it in PiCorePlayer 5.0, the screen is correctly detected for display, but I have no touchscreen.
In the piCorePlayer menu (accessed trough keyboard) the option "adjust LCD brightness" I always get "no official raspberry pi display found" (or something to that end)

Where do we find the correct drivers to install for touchscreen and brightness control?

Thanks.