EVCHAN_IMPL_HNDL
subp->ev_subhead = EVCHAN_IMPL_HNDL(scp);
evchan_impl_hdl_t *hdl = EVCHAN_IMPL_HNDL(scp);
#define EV_PID(evcp) (EVCHAN_IMPL_HNDL(evcp)->ev_pid)
#define EV_FD(evcp) (EVCHAN_IMPL_HNDL(evcp)->ev_fd)
#define EV_LOCK(evcp) (&(EVCHAN_IMPL_HNDL(evcp)->ev_lock))
#define EV_SUB(evcp) (&(EVCHAN_IMPL_HNDL(evcp)->ev_sub))
#define EV_SUB_NEXT(evcp) (EVCHAN_IMPL_HNDL(evcp)->ev_sub.evchan_sub_next)