NAME | SYNOPSIS | CONFIGURATION | DESCRIPTION | FILES | SEE ALSO | COLOPHON
LP(4) Linux Programmer's Manual LP(4)
lp - line printer devices
#include <linux/lp.h>
lp[0-2] are character devices for the parallel line printers; they have major
number 6 and minor number 0-2. The minor numbers correspond to the printer
port base addresses 0x03bc, 0x0378 and 0x0278. Usually they have mode 220 and
are owned by root and group 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 usual dot matrix printers polling will
usually be enough. The default is polling.
The following ioctl(2) calls are supported:
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 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 only influences the polling driver.
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 arg. If printing is too slow, increase this number; if
the system gets too slow, decrease this number. The default is 1000.
It only influences the polling driver.
int ioctl(int fd, LPABORT, int arg)
If arg is 0, the printer driver will retry on errors, otherwise it will
abort. The default is 0.
int ioctl(int fd, LPABORTOPEN, int arg)
If arg is 0, open(2) will be aborted on error, otherwise error will be
ignored. The default is to ignore it.
int ioctl(int fd, LPCAREFUL, int arg)
If 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.
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 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. This is used for both the polling and
the interrupt driver.
int ioctl(int fd, LPSETIRQ, int arg)
This ioctl(2) requires superuser privileges. It takes an int
containing the new IRQ as argument. As a side effect, the printer will
be reset. When arg is 0, the polling driver will be used, which is
also default.
int ioctl(int fd, LPGETIRQ, int *arg)
Stores the currently used IRQ in arg.
int ioctl(int fd, LPGETSTATUS, int *arg)
Stores the value of the status port in arg. The bits have the
following meaning:
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
Refer to your printer manual for the meaning of the signals. Note that
undocumented bits may also be set, depending on your printer.
int ioctl(int fd, LPRESET)
Resets the printer. No argument is used.
/dev/lp*
chmod(1), chown(1), mknod(1), lpcntl(8), tunelp(8)
This page is part of release 3.23 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
Linux 1995-01-15 LP(4)