Seatd is a minimal seat management daemon, and a universal seat management library. Seat management takes care of mediating access to shared devices (graphics, input), without requiring applications like Wayland compositors being granted root privileges.
USE flags for sys-auth/seatd Minimal seat management daemon and universal library
emerge --ask sys-auth/seatd
Add the seatd daemon to the default runlevel so that seat management is provided on system startup:
rc-update add seatd default
Start the seatd daemon now:
rc-service seatd start