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+'\" t
+.\" Copyright (c) Michael Haardt (michael@cantor.informatik.rwth-aachen.de),
+.\" Sun Jan 15 19:16:33 1995
+.\"
+.\" SPDX-License-Identifier: GPL-2.0-or-later
+.\"
+.\" Modified, Sun Feb 26 15:02:58 1995, faith@cs.unc.edu
+.TH lp 4 2024-05-02 "Linux man-pages (unreleased)"
+.SH NAME
+lp \- line printer devices
+.SH SYNOPSIS
+.nf
+.B #include <linux/lp.h>
+.fi
+.SH CONFIGURATION
+\fBlp\fP[0\[en]2] are character devices for the parallel line printers;
+they have major number 6 and minor number 0\[en]2.
+The minor numbers
+correspond to the printer port base addresses 0x03bc, 0x0378, and 0x0278.
+Usually they have mode 220 and are owned by user
+.I root
+and group
+.IR lp .
+You can use printer ports either with polling or with interrupts.
+Interrupts are recommended when high traffic is expected, for example,
+for laser printers.
+For typical dot matrix printers, polling will usually be enough.
+The default is polling.
+.SH DESCRIPTION
+The following
+.BR ioctl (2)
+calls are supported:
+.TP
+.BR "int ioctl(int " fd ", LPTIME, int " arg )
+Sets the amount of time that the driver sleeps before rechecking the printer
+when the printer's buffer appears to be filled to
+.IR arg .
+If you have a fast printer, decrease this number;
+if you have a slow printer, then increase it.
+This is in hundredths of a second, the default 2
+being 0.02 seconds.
+It influences only the polling driver.
+.TP
+.BR "int ioctl(int " fd ", LPCHAR, int " arg )
+Sets the maximum number of busy-wait iterations which the polling driver does
+while waiting for the printer to get ready for receiving a character to
+.IR arg .
+If printing is too slow, increase this number; if the
+system gets too slow, decrease this number.
+The default is 1000.
+It influences only the polling driver.
+.TP
+.BR "int ioctl(int " fd ", LPABORT, int " arg )
+If
+.I arg
+is 0, the printer driver will retry on errors, otherwise
+it will abort.
+The default is 0.
+.TP
+.BR "int ioctl(int " fd ", LPABORTOPEN, int " arg )
+If
+.I arg
+is 0,
+.BR open (2)
+will be aborted on error, otherwise error will be ignored.
+The default is to ignore it.
+.TP
+.BR "int ioctl(int " fd ", LPCAREFUL, int " arg )
+If
+.I arg
+is 0, then the out-of-paper, offline, and error signals are
+required to be false on all writes, otherwise they are ignored.
+The default is to ignore them.
+.TP
+.BR "int ioctl(int " fd ", LPWAIT, int " arg )
+Sets the number of busy waiting iterations to wait before strobing the
+printer to accept a just-written character, and the number of iterations to
+wait before turning the strobe off again,
+to
+.IR arg .
+The specification says this time should be 0.5
+microseconds, but experience has shown the delay caused by the code is
+already enough.
+For that reason, the default value is 0.
+.\" FIXME . Actually, since Linux 2.2, the default is 1
+This is used for both the polling and the interrupt driver.
+.TP
+.BR "int ioctl(int " fd ", LPSETIRQ, int " arg )
+This
+.BR ioctl (2)
+requires superuser privileges.
+It takes an
+.I int
+containing the new IRQ as argument.
+As a side effect, the printer will be reset.
+When
+.I arg
+is 0, the polling driver will be used, which is also default.
+.TP
+.BR "int ioctl(int " fd ", LPGETIRQ, int *" arg )
+Stores the currently used IRQ in
+.IR arg .
+.TP
+.BR "int ioctl(int " fd ", LPGETSTATUS, int *" arg )
+Stores the value of the status port in
+.IR arg .
+The bits have the following meaning:
+.TS
+l l.
+LP_PBUSY inverted busy input, active high
+LP_PACK unchanged acknowledge input, active low
+LP_POUTPA unchanged out-of-paper input, active high
+LP_PSELECD unchanged selected input, active high
+LP_PERRORP unchanged error input, active low
+.TE
+.IP
+Refer to your printer manual for the meaning of the signals.
+Note that undocumented bits may also be set, depending on your printer.
+.TP
+.BR "int ioctl(int " fd ", LPRESET)"
+Resets the printer.
+No argument is used.
+.SH FILES
+.I /dev/lp*
+.\" .SH AUTHORS
+.\" The printer driver was originally written by Jim Weigand and Linus
+.\" Torvalds.
+.\" It was further improved by Michael K.\& Johnson.
+.\" The interrupt code was written by Nigel Gamble.
+.\" Alan Cox modularized it.
+.\" LPCAREFUL, LPABORT, LPGETSTATUS were added by Chris Metcalf.
+.SH SEE ALSO
+.BR chmod (1),
+.BR chown (1),
+.BR mknod (1),
+.BR lpcntl (8),
+.BR tunelp (8)