LP(4)							     Linux Programmer's Manual							     LP(4)

NAME

       lp - line printer devices

SYNOPSIS

       #include <linux/lp.h>

CONFIGURATION

       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.

DESCRIPTION

       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 receiv-
	      ing  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.

FILES

       /dev/lp*

SEE ALSO

       chmod(1), chown(1), mknod(1), lpcntl(8), tunelp(8)

COLOPHON

       This page is part of release 3.44 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)