tb_find_tunnel
tunnel = tb_find_tunnel(tb, TB_TUNNEL_DP, in, NULL);
tunnel = tb_find_tunnel(group->tb, TB_TUNNEL_DP, in, NULL);
tunnel = tb_find_tunnel(tb, TB_TUNNEL_DP, in, out);
tunnel = tb_find_tunnel(tb, TB_TUNNEL_PCI, NULL, up);
tunnel = tb_find_tunnel(tb, TB_TUNNEL_DP, in, NULL);
return tb_find_tunnel(tb, TB_TUNNEL_USB3, usb3_down, NULL);