.\" Copyright (c) 1986, 1991, 1993.\"	The Regents of the University of California.  All rights reserved..\".\" Redistribution and use in source and binary forms, with or without.\" modification, are permitted provided that the following conditions.\" are met:.\" 1. Redistributions of source code must retain the above copyright.\"    notice, this list of conditions and the following disclaimer..\" 2. Redistributions in binary form must reproduce the above copyright.\"    notice, this list of conditions and the following disclaimer in the.\"    documentation and/or other materials provided with the distribution..\" 3. All advertising materials mentioning features or use of this software.\"    must display the following acknowledgement:.\"	This product includes software developed by the University of.\"	California, Berkeley and its contributors..\" 4. Neither the name of the University nor the names of its contributors.\"    may be used to endorse or promote products derived from this software.\"    without specific prior written permission..\".\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION).\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF.\" SUCH DAMAGE..\".\"     @(#)tb.4	8.1 (Berkeley) 6/5/93.\".Dd June 5, 1993.Dt TB 4 vax.Os BSD 4.3.Sh NAME.Nm tb.Nd line discipline for digitizing devices.Sh SYNOPSIS.Cd pseudo-device tb.Sh DESCRIPTIONThis line discipline provides a polled interface to many commondigitizing devices which are connected to a host through a serial line.When these devices stream data at high speed, the use of theline discipline is critical in minimizing the number of samplesthat would otherwise be lost due to buffer exhaustion in the.Xr tty 4handler..PpThe line discipline is enabled by a sequence:.Bd -literal -offset indent#include <sys/tablet.h>int ldisc = TBLDISC, fildes; ...ioctl(fildes, TIOCSETD, &ldisc);.Ed.PpA typical application program then polls the digitizing device byreading a binary data structure which contains: the current X andY positions (in the device coordinate space),up-down status of the buttons or pen stylus,proximity information (when available), and a countof the number of samples received from the input devicesince it was opened.  In addition, devices such as the.Tn GTCOappend tilt and pressure information to the end ofthe aforementioned structure.  For the Polhemus 3-D digitizerthe structure read is completely different. Refer to theinclude file for a complete description..PpWhile in tablet mode, normal teletype input and output functions take place.Thus, if an 8 bit output data path is desired, it is necessaryto prepare the output line by putting it into.Tn RAWmode using.Xr ioctl 2 .This must be done.Em beforechanging the discipline with.Dv TIOCSETD ,as most.Xr ioctl 2calls are disabled while in tablet line-discipline mode..PpThe line discipline supports.Xr ioctl 2requests to get/set the operating mode, and to get/set the tablet typeand operating mode by.Em or Ns -ingthe two values together..PpThe line discipline supports digitizing devices which arecompatible with Hitachi,.Tn GTCO ,or Polhemus protocol formats.For Hitachi there are several formats with that used in thenewer model.Tn HDG-1111Bthe most common..Sh DIAGNOSTICSNone..Sh SEE ALSO.Xr tty 4.Sh HISTORYThe.Nminterface appeared in.Bx 4.3 .