HelenOS sources
client_connection 906 uspace/srv/hid/console/console.c async_set_fallback_port_handler(client_connection, NULL);
client_connection 902 uspace/srv/hid/input/input.c async_set_fallback_port_handler(client_connection, NULL);
client_connection 481 uspace/srv/hid/output/output.c async_set_fallback_port_handler(client_connection, NULL);
client_connection 356 uspace/srv/hid/remcons/remcons.c async_set_fallback_port_handler(client_connection, NULL);
client_connection 483 uspace/srv/hid/rfb/main.c async_set_fallback_port_handler(client_connection, &rfb);
HelenOS homepage, sources at GitHub