LP(4)                     (2020-08-13)                      LP(4)

          lp - line printer devices

          #include <linux/lp.h>

          lp[0en2] are character devices for the parallel line print-
          ers; they have major number 6 and minor number 0en2.  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, pol-
          ling 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 influ-
               ences 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 sys-
               tem 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, other-
               wise error will be ignored.  The default is to ignore

          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, other-
               wise they are ignored.  The default is to ignore them.

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     LP(4)                     (2020-08-13)                      LP(4)

          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 experi-
               ence 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: 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_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 5.10 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 https://www.kernel.org/doc/man-pages/.

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