RaspberryPi 4 GPIO

[satch <netbsd-lists%protonmail.com@localhost>]

I used the NetBSD 10.1 arm64.img.gz with a RPi4 model B 8Gb.

I would like to use a GPIO pin for output. 
However this does not seem to be supported by the GENERIC kernel.

eg. 'dmesg | grep gpio' returns nothing.

Could I please get advice on how to proceed?

Thanks,
Satch