code: def halt(self, request_type):
          
          try:
              if request_type & ch9.USB_DIR_IN:
                  self.read(0)
              else:
                  self.write(b'')
          except IOError as exc:
              if exc.errno != errno.EL2HLT:
                  raise
          else:
              raise ValueError('halt did not return EL2HLT ?')
docs: Halt current endpoint.