.\" This file Copyright (C) 1992-1997 Michael K. Johnson <johnsonm@redhat.com>
.\" It may be distributed under the terms of the GNU General Public License,
.\" version 2, or any higher version.  See section COPYING of the GNU General
.\" Public license for conditions under which this file may be redistributed.
.\" $Id: tunelp.8,v 1.6 1997/06/20 16:10:35 janl Exp $
.TH tunelp 8 "26 August 1992" "Cohesive Systems" "Linux Programmer's Manual"
.SH NAME
tunelp \- set various parameters for the lp device
.SH SYNOPSIS
\fBtunelp\fP \fI<device>\fP [-i \fI<IRQ>\fP | -t \fI<TIME>\fP | -c \fI<CHARS>\fP | -w \fI<WAIT>\fP | -a [on|off] | -o [on|off] | -C [on|off] | -r | -s | -q [on|off] ]
.SH DESCRIPTION
\fBtunelp\fP sets several parameters for the /dev/lp\fI?\fP devices, for better
performance (or for any performance at all, if your printer won't work
without it...)  Without parameters, tells whether the device is using
interrups, and if so, which one.  With parameters, sets the device
characteristics accordingly.  The parameters are as follows:

-i \fI<IRQ>\fP is the IRQ to use for the parallel port in question.  If this
is set to something non-zero, -t and -c have no effect.  If your port
does not use interrupts, this option will make printing stop.
.B tunelp -i 0
restores non-interrupt driven (polling) action, and your printer should
work again.  If your parallel port does support interrupts,
interrupt-driven printing should be somewhat faster and efficient, and
will probably be desireable.

-t \fI<TIME>\fP is the amount of time in jiffies that the driver waits if the
printer doesn't take a character for the number of tries dictated by
the -c parameter.  10 is the default value.  If you want fastest
possible printing, and don't care about system load, you may set this
to 0.  If you don't care how fast your printer goes, or are printing
text on a slow printer with a buffer, then 500 (5 seconds) should be
fine, and will give you very low system load.  This value generally
should be lower for printing graphics than text, by a factor of
approximately 10, for best performance.

-c \fI<CHARS>\fP is the number of times to try to output a character to the
printer before sleeping for -t \fI<TIME>\fP.  It is the number of times around
a loop that tries to send a character to the printer.  120 appears to
be a good value for most printers.  250 is the default, because there
are some printers that require a wait this long, but feel free to
change this.  If you have a very fast printer like an HP laserjet 4, a
value of 10 might make more sense.  If you have a \fIreally\fP old
printer, you can increase this farther.

Setting -t \fI<TIME>\fP to 0 is equivalent to setting -c \fI<CHARS>\fP
to infinity.

-w \fI<WAIT>\fP is the a busy loop counter for the strobe signal.  While most
printers appear to be able to deal with an extremely short strobe,
some printers demand a longer one.  Increasing this from the default
0 may make it possible to print with those printers.  This may also
make it possible to use longer cables.

-a [on|off] This is whether to abort on printer error -- the default
is not to.  If you are sitting at your computer, you probably want to
be able to see an error and fix it, and have the printer go on
printing.  On the other hand, if you aren't, you might rather that
your printer spooler find out that the printer isn't ready, quit
trying, and send you mail about it.  The choice is yours.

-o [on|off] This option is much like -a.  It makes any open() of this
device check to see that the device is on-line and not reporting any
out of paper or other errors.  This is the correct setting for most
versions of lpd.

-C [on|off] This option adds extra ("careful") error checking.  When
this option is on, the printer driver will ensure that the printer is
on-line and not reporting any out of paper or other errors before
sending data.  This is particularly useful for printers that normally
appear to accept data when turned off.

-s This option returns the current printer status, both as a 
decimal number from 0..255, and as a list of active flags.  When
this option is specified, -q off, turning off the display of the
current IRQ, is implied.

-o, -C, and -s all require a Linux kernel version of 1.1.76 or later.

-r This option resets the port.  It requires a Linux kernel version of
1.1.80 or later.

-q [on|off] This option sets printing the display of the current IRQ
setting.