1.\" Copyright (c) 2001 2.\" The FreeBSD Project 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 10.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 11.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 12.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 13.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 14.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 15.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 16.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 17.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 18.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 19.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 20.\" SUCH DAMAGE. 21.\" 22.\" $FreeBSD$ 23.\" 24.Dd January 27, 2005 25.Dt NMDM 4 26.Os 27.Sh NAME 28.Nm nmdm 29.Nd nullmodem terminal driver 30.Sh SYNOPSIS 31.Cd "device nmdm" 32.Sh DESCRIPTION 33The 34.Nm 35driver provides two 36.Xr tty 4 37devices connected 38by a virtual 39.Dq "null modem" 40cable. 41.Pp 42If either of the two tty devices have the 43.Dv CDSR_OFLOW 44bit 45.Pq Dq Li "stty dsrflow" 46set in their line discipline, the 47.Nm 48device will emulate the speed configured in the 49.Xr termios 4 50settings. 51The speed emulation works independently in the two directions, 52controlled by the slower end's termios settings 53.Va ( c_ispeed , c_ospeed , 54.Dv CS5 ... CS8 , CSTOPB 55and 56.Dv PARENB ) . 57.Sh FILES 58.Bl -tag -width ".Pa /dev/nmdm Ns Ar N Ns Op Pa AB" -compact 59.It Pa /dev/nmdm Ns Ar N Ns Op Pa AB 60nullmodem device nodes. 61Where the 62.Pa A 63node has a matching 64.Pa B 65node. 66.El 67.Pp 68The 69.Nm 70driver implements 71.Dq "on-demand device creation" 72so simply accessing a given instance in 73.Pa /dev 74will create it. 75.Sh DIAGNOSTICS 76None. 77.Sh SEE ALSO 78.Xr stty 1 , 79.Xr termios 4 , 80.Xr tty 4 81.Sh HISTORY 82The 83.Nm 84driver first appeared in 85.Fx 4.4 . 86