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 23, 2018 25.Dt NMDM 4 26.Os 27.Sh NAME 28.Nm nmdm 29.Nd nullmodem terminal driver 30.Sh SYNOPSIS 31To compile this driver into the kernel, 32place the following line in your 33kernel configuration file: 34.Bd -ragged -offset indent 35.Cd "device nmdm" 36.Ed 37.Pp 38Alternatively, to load the driver as a 39module at boot time, place the following line in 40.Xr loader.conf 5 : 41.Bd -literal -offset indent 42nmdm_load="YES" 43.Ed 44.Sh DESCRIPTION 45The 46.Nm 47driver provides two 48.Xr tty 4 49devices connected 50by a virtual 51.Dq "null modem" 52cable. 53.Pp 54If either of the two tty devices have the 55.Dv CDSR_OFLOW 56bit 57.Pq Dq Li "stty dsrflow" 58set in their line discipline, the 59.Nm 60device will emulate the speed configured in the 61.Xr termios 4 62settings. 63The speed emulation works independently in the two directions, 64controlled by the slower end's termios settings 65.Va ( c_ispeed , c_ospeed , 66.Dv CS5 ... CS8 , CSTOPB 67and 68.Dv PARENB ) . 69.Sh FILES 70.Bl -tag -width ".Pa /dev/nmdm Ns Ar N Ns Op Pa AB" -compact 71.It Pa /dev/nmdm Ns Ar N Ns Op Pa AB 72nullmodem device nodes. 73Where the 74.Pa A 75node has a matching 76.Pa B 77node. 78.El 79.Pp 80The 81.Nm 82driver implements 83.Dq "on-demand device creation" 84so simply accessing a given instance in 85.Pa /dev 86will create it. 87.Sh DIAGNOSTICS 88None. 89.Sh SEE ALSO 90.Xr stty 1 , 91.Xr termios 4 , 92.Xr tty 4 93.Sh HISTORY 94The 95.Nm 96driver first appeared in 97.Fx 4.4 . 98