al_get_haptic_from_keyboard man page
al_get_haptic_from_keyboard — Allegro 5 API
#include <allegro5/allegro.h> ALLEGRO_HAPTIC *al_get_haptic_from_keyboard(ALLEGRO_KEYBOARD *dev)
If the keyboard has haptic capabilities, returns the associated haptic device handle. Otherwise returns NULL.
[Unstable API]: Perhaps could be simplified due to limited support for all the exposed features across all of the platforms. Awaiting feedback from users.