ev_io_set
ev_io_set (&pipe_w, evpipe [0] < 0 ? evpipe [1] : evpipe [0], EV_READ);
ev_io_set (&fs_w, fs_fd, EV_READ);
ev_io_set (&once->io, fd, events);
#define ev_io_init(ev,cb,fd,events) do { ev_init ((ev), (cb)); ev_io_set ((ev),(fd),(events)); } while (0)
ev_io_set(((ev_io*) evpriv), verto_get_fd(ev), events);
ev_io_set(((ev_io*) evpriv), verto_get_fd(ev), events);