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  typical  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 influences  only
          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 influences only 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
          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

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




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


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