mirror of https://github.com/mkerrisk/man-pages
146 lines
5.2 KiB
Groff
146 lines
5.2 KiB
Groff
.\" Copyright (c) Michael Haardt (michael@cantor.informatik.rwth-aachen.de),
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.\" Sun Jan 15 19:16:33 1995
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.\"
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.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, see
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.\" <http://www.gnu.org/licenses/>.
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.\" %%%LICENSE_END
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.\"
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.\" Modified, Sun Feb 26 15:02:58 1995, faith@cs.unc.edu
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.TH LP 4 2021-03-22 "Linux" "Linux Programmer's Manual"
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.SH NAME
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lp \- line printer devices
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.SH SYNOPSIS
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.nf
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.B #include <linux/lp.h>
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.fi
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.SH CONFIGURATION
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\fBlp\fP[0\(en2] are character devices for the parallel line printers;
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they have major number 6 and minor number 0\(en2.
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The minor numbers
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correspond to the printer port base addresses 0x03bc, 0x0378, and 0x0278.
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Usually they have mode 220 and are owned by user
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.I root
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and group
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.IR lp .
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You can use printer ports either with polling or with interrupts.
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Interrupts are recommended when high traffic is expected, for example,
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for laser printers.
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For typical dot matrix printers, polling will usually be enough.
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The default is polling.
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.SH DESCRIPTION
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The following
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.BR ioctl (2)
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calls are supported:
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.IP "\fBint ioctl(int \fP\fIfd\fP\fB, LPTIME, int \fP\fIarg\fP\fB)\fP"
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Sets the amount of time that the driver sleeps before rechecking the printer
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when the printer's buffer appears to be filled to
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.IR arg .
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If you have a fast printer, decrease this number;
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if you have a slow printer, then increase it.
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This is in hundredths of a second, the default 2
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being 0.02 seconds.
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It influences only the polling driver.
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.IP "\fBint ioctl(int \fP\fIfd\fP\fB, LPCHAR, int \fP\fIarg\fP\fB)\fP"
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Sets the maximum number of busy-wait iterations which the polling driver does
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while waiting for the printer to get ready for receiving a character to
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.IR arg .
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If printing is too slow, increase this number; if the
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system gets too slow, decrease this number.
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The default is 1000.
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It influences only the polling driver.
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.IP "\fBint ioctl(int \fP\fIfd\fP\fB, LPABORT, int \fP\fIarg\fP\fB)\fP"
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If
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.I arg
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is 0, the printer driver will retry on errors, otherwise
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it will abort.
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The default is 0.
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.IP "\fBint ioctl(int \fP\fIfd\fP\fB, LPABORTOPEN, int \fP\fIarg\fP\fB)\fP"
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If
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.I arg
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is 0,
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.BR open (2)
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will be aborted on error, otherwise error will be ignored.
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The default is to ignore it.
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.IP "\fBint ioctl(int \fP\fIfd\fP\fB, LPCAREFUL, int \fP\fIarg\fP\fB)\fP"
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If
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.I arg
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is 0, then the out-of-paper, offline, and error signals are
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required to be false on all writes, otherwise they are ignored.
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The default is to ignore them.
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.IP "\fBint ioctl(int \fP\fIfd\fP\fB, LPWAIT, int \fP\fIarg\fP\fB)\fP"
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Sets the number of busy waiting iterations to wait before strobing the
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printer to accept a just-written character, and the number of iterations to
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wait before turning the strobe off again,
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to
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.IR arg .
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The specification says this time should be 0.5
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microseconds, but experience has shown the delay caused by the code is
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already enough.
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For that reason, the default value is 0.
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.\" FIXME . Actually, since Linux 2.2, the default is 1
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This is used for both the polling and the interrupt driver.
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.IP "\fBint ioctl(int \fP\fIfd\fP\fB, LPSETIRQ, int \fP\fIarg\fP\fB)\fP"
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This
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.BR ioctl (2)
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requires superuser privileges.
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It takes an
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.I int
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containing the new IRQ as argument.
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As a side effect, the printer will be reset.
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When
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.I arg
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is 0, the polling driver will be used, which is also default.
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.IP "\fBint ioctl(int \fP\fIfd\fP\fB, LPGETIRQ, int *\fP\fIarg\fP\fB)\fP"
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Stores the currently used IRQ in
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.IR arg .
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.IP "\fBint ioctl(int \fP\fIfd\fP\fB, LPGETSTATUS, int *\fP\fIarg\fP\fB)\fP"
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Stores the value of the status port in
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.IR arg .
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The bits have the following meaning:
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.TS
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l l.
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LP_PBUSY inverted busy input, active high
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LP_PACK unchanged acknowledge input, active low
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LP_POUTPA unchanged out-of-paper input, active high
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LP_PSELECD unchanged selected input, active high
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LP_PERRORP unchanged error input, active low
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.TE
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.IP
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Refer to your printer manual for the meaning of the signals.
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Note that undocumented bits may also be set, depending on your printer.
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.IP "\fBint ioctl(int \fP\fIfd\fP\fB, LPRESET)\fP"
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Resets the printer.
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No argument is used.
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.SH FILES
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.I /dev/lp*
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.\" .SH AUTHORS
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.\" The printer driver was originally written by Jim Weigand and Linus
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.\" Torvalds.
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.\" It was further improved by Michael K.\& Johnson.
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.\" The interrupt code was written by Nigel Gamble.
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.\" Alan Cox modularized it.
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.\" LPCAREFUL, LPABORT, LPGETSTATUS were added by Chris Metcalf.
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.SH SEE ALSO
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.BR chmod (1),
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.BR chown (1),
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.BR mknod (1),
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.BR lpcntl (8),
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.BR tunelp (8)
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