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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  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 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(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.




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


     This page is part of release 4.16 of the Linux  man-pages  project.   A
     description  of  the project, information about reporting bugs, and the
     latest    version    of    this    page,    can     be     found     at

Linux 1995-01-15 LP(4)

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