freebsd-skq/share/man/man4/nmdm.4
allanjude 97ffdc179c Add cross references betwen ttys(5) and related drivers
nmdm(4), ucom(4), and uart(4)

PR:		247638
Submitted by:	Pau Amma <pauamma@gundo.com>
Reported by:	0mp
MFC after:	4 weeks
Sponsored by:	Klara Inc.
Event:		July 2020 Bugathon
2020-07-11 20:56:57 +00:00

99 lines
2.4 KiB
Groff

.\" Copyright (c) 2001
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.\" $FreeBSD$
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.Dd July 11, 2020
.Dt NMDM 4
.Os
.Sh NAME
.Nm nmdm
.Nd nullmodem terminal driver
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following line in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device nmdm"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
nmdm_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
driver provides two
.Xr tty 4
devices connected
by a virtual
.Dq "null modem"
cable.
.Pp
If either of the two tty devices have the
.Dv CDSR_OFLOW
bit
.Pq Dq Li "stty dsrflow"
set in their line discipline, the
.Nm
device will emulate the speed configured in the
.Xr termios 4
settings.
The speed emulation works independently in the two directions,
controlled by the slower end's termios settings
.Va ( c_ispeed , c_ospeed ,
.Dv CS5 ... CS8 , CSTOPB
and
.Dv PARENB ) .
.Sh FILES
.Bl -tag -width ".Pa /dev/nmdm Ns Ar N Ns Op Pa AB" -compact
.It Pa /dev/nmdm Ns Ar N Ns Op Pa AB
nullmodem device nodes.
Where the
.Pa A
node has a matching
.Pa B
node.
.El
.Pp
The
.Nm
driver implements
.Dq "on-demand device creation"
so simply accessing a given instance in
.Pa /dev
will create it.
.Sh DIAGNOSTICS
None.
.Sh SEE ALSO
.Xr stty 1 ,
.Xr termios 4 ,
.Xr tty 4 ,
.Xr ttys 5
.Sh HISTORY
The
.Nm
driver first appeared in
.Fx 4.4 .