141 lines
5.0 KiB
Groff
141 lines
5.0 KiB
Groff
.\" Copyright (c) 1996-1999 Whistle Communications, Inc.
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.\" All rights reserved.
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.\"
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.\" Subject to the following obligations and disclaimer of warranty, use and
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.\" redistribution of this software, in source or object code forms, with or
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.\" without modifications are expressly permitted by Whistle Communications;
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.\" provided, however, that:
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.\" 1. Any and all reproductions of the source or object code must include the
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.\" copyright notice above and the following disclaimer of warranties; and
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.\" 2. No rights are granted, in any manner or form, to use Whistle
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.\" Communications, Inc. trademarks, including the mark "WHISTLE
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.\" COMMUNICATIONS" on advertising, endorsements, or otherwise except as
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.\" such appears in the above copyright notice or in the software.
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.\"
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.\" THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
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.\" TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
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.\" REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
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.\" INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
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.\" WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
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.\" REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
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.\" SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
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.\" IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
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.\" RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
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.\" WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
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.\" PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
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.\" SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
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.\" OF SUCH DAMAGE.
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.\"
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.\" Author: Archie Cobbs <archie@FreeBSD.org>
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.\"
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.\" $FreeBSD$
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.\" $Whistle: ng_tty.8,v 1.5 1999/01/25 23:46:28 archie Exp $
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.\"
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.Dd January 19, 1999
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.Dt NG_TTY 4
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.Os FreeBSD
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.Sh NAME
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.Nm ng_tty
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.Nd netgraph node type that is also a line discipline
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.Sh SYNOPSIS
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.Fd #include <sys/ttycom.h>
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.Fd #include <netgraph/ng_message.h>
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.Fd #include <netgraph/ng_tty.h>
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.Sh DESCRIPTION
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The
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.Nm tty
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node type is both a netgraph node type and a line discipline.
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A new node is created when the corresponding line discipline,
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.Dv NETGRAPHDISC ,
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is registered on a tty device (see
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.Xr tty 4 ) .
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.Pp
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The node has a single hook called
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.Dv hook .
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Incoming bytes received on the tty device are sent out on this hook,
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and frames received on
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.Dv hook
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are transmitted out on the tty device.
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No modification to the data is performed in either direction.
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While the line discipline is installed on a tty, the normal
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read and write operations are unavailable, returning
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.Er EIO .
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.Pp
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The node supports an optional
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.Dq hot character .
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If set to non-zero, incoming
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data from the tty device is queued until this character is seen.
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This avoids sending lots of mbufs containing a small number of bytes,
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but introduces potentially infinite latency.
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The default hot character is 0x7e, consistent with
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.Dv hook
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being connected to a
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.Xr ng_async 4
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type node. The hot character has no effect on the transmission of data.
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.Pp
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The node will attempt to give itself the same netgraph name as the name
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of the tty device.
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In any case, information about the node is available via the netgraph
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.Xr ioctl 2
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command
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.Dv NGIOCGINFO .
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This command returns a
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.Dv "struct nodeinfo"
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similar to the
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.Dv NGM_NODEINFO
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netgraph control message.
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.Sh HOOKS
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This node type supports the following hooks:
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.Pp
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.Bl -tag -width foobar
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.It Dv hook
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.Xr tty 4
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serial data contained in
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.Dv mbuf
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structures, with arbitrary inter-frame boundaries.
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.El
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.Sh CONTROL MESSAGES
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This node type supports the generic control messages, plus the following:
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.Bl -tag -width foo
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.It Dv NGM_TTY_SET_HOTCHAR
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This command takes an integer argument and sets the hot character
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from the lower 8 bits. A hot character of zero disables queueing,
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so that all received data is forwarded immediately.
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.It Dv NGM_TTY_GET_HOTCHAR
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Returns an integer containing the current hot character in the lower
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eight bits.
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.El
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.Sh SHUTDOWN
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This node shuts down when the corresponding device is closed
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(or the line discipline is uninstalled on the device).
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The
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.Dv NGM_SHUTDOWN
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control message is not valid, and always returns the error
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.Er EOPNOTSUPP .
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.Sh BUGS
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The serial driver code also has a notion of a
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.Dq hot character .
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Unfortunately, this value is statically defined in terms of the
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line discipline and cannot be changed.
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Therefore, if a hot character other than 0x7e (the default) is set for the
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.Nm
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node, the node has no way to convey this information to the
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serial driver, and sub-optimal performance may result.
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.Sh SEE ALSO
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.Xr ioctl 2 ,
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.Xr netgraph 4 ,
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.Xr tty 4 ,
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.Xr ng_async 4 ,
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.Xr ngctl 8
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.Sh HISTORY
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The
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.Nm
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node type was implemented in
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.Fx 4.0 .
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.Sh AUTHORS
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.An Archie Cobbs Aq archie@FreeBSD.org
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