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       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 user 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 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.




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


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