umad_close_port - close InfiniBand device port for umad access
       #include <infiniband/umad.h>
       int umad_close_port(int portid);
       umad_close_port() closes the port specified by the handle portid.
       umad_close_port()  returns 0 on success, and a negative value on error.
       -EINVAL is returned if the portid is not a handle  to  a  valid  (open)
       port.
       umad_open_port(3)
       Hal Rosenstock <halr@voltaire.com>