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

       lp - line printer devices

       #include <&lt;linux/lp.h>&gt;

       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,  e.g.  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

       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 strob-
              ing the printer to accept a just-written character, and the num-
              ber 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() 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:

              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_PSE-
              LECD     unchanged   selected   input,   active   high   LP_PER-
              RORP     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

       int ioctl(int fd, LPRESET)
              Resets the printer.  No argument is used.


       The printer driver was originally written by Jim Weigand and Linus Tor-
       valds.   It  was further improved by Michael K. Johnson.  The interrupt
       code was written by Nigel Gamble.  Alan Cox modularised it.  LPCAREFUL,
       LPABORT, LPGETSTATUS were added by Chris Metcalf.

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

Special files                     1995-01-15                             LP(4)