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 recom-
       mended when high traffic is expected, for example, for laser printers.  For usual dot matrix printers polling  will  usu-
       ally 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 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, depend-
              ing 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 3.25 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)