tunelp - set various parameters for the lp device


SYNOPSIS

       tunelp  <device>  [-i  <IRQ> | -t <TIME> | -c <CHARS> | -w
       <WAIT> | -a [on|off] | -o [on|off] | -C [on|off] | -r | -s
       | -q [on|off] | - T [on|off] ]


DESCRIPTION

       tunelp  sets  several parameters for the /dev/lp? devices,
       for better performance (or for any performance at all,  if
       your  printer  won't  work without it...)  Without parame­
       ters, it tells whether the device is using interrupts, and
       if  so,  which  one.   With parameters, it sets the device
       characteristics accordingly.  The parameters are  as  fol­
       lows:

       -i <IRQ>
              specifies  the  IRQ to use for the parallel port in
              question.  If this is set to something non-zero, -t
              and  -c  have no effect.  If your port does not use
              interrupts, this option will  make  printing  stop.
              The  command  tunelp  -i  0  restores non-interrupt
              driven (polling) action, and  your  printer  should
              work  again.   If  your  parallel port does support
              interrupts,  interrupt-driven  printing  should  be
              somewhat faster and efficient, and will probably be
              desirable.

              NOTE: This option will have no effect  with  kernel
              2.1.131  or  later  since the irq is handled by the
              parport driver. You can change the parport irq  for
              example      via     /proc/parport/*/irq.      Read
              /usr/src/linux/Documentation/parport.txt  for  more
              details on parport.

       -t <TIME>
              is  the  amount  of time in jiffies that the driver
              waits if the printer doesn't take a  character  for
              the  number  of tries dictated by the -c parameter.
              10 is the default value.  If you want fastest  pos­
              sible  printing,  and don't care about system load,
              you may set this to 0.  If you don't care how  fast
              your  printer  goes, or are printing text on a slow
              printer with a buffer, then 500 (5 seconds)  should
              be  fine,  and  will give you very low system load.
              This value generally should be lower  for  printing
              graphics  than  text,  by a factor of approximately
              10, for best performance.

              is the number of times to try to output a character
              to  the  printer before sleeping for -t <TIME>.  It
              is the number of times around a loop that tries  to
              send a character to the printer.  120 appears to be
              a good value for most  printers  in  polling  mode.
              1000  is the default, because there are some print­
              ers that become jerky otherwise, but you  must  set
              this to `1' to handle the maximal CPU efficiency if
              you are using interrupts. If you have a  very  fast
              printer,  a  value of 10 might make more sense even
              if in polling mode.   If  you  have  a  really  old
              printer, you can increase this further.

              Setting  -t <TIME> to 0 is equivalent to setting -c
              <CHARS> to infinity.

       -w <WAIT>
              is the number of usec we wait  while  playing  with
              the  strobe  signal.  While most printers appear to
              be able to deal with  an  extremely  short  strobe,
              some printers demand a longer one.  Increasing this
              from the default 1 may make it  possible  to  print
              with  those printers.  This may also make it possi­
              ble to use longer cables.  It's  also  possible  to
              decrease  this  value  to 0 if your printer is fast
              enough or your machine is slow enough.

       -a [on|off]
              This is whether to abort on  printer  error  -  the
              default is not to.  If you are sitting at your com­
              puter, you probably want to be able to see an error
              and  fix  it,  and have the printer go on printing.
              On the other hand, if you aren't, you might  rather
              that your printer spooler find out that the printer
              isn't ready, quit trying, and send you  mail  about
              it.  The choice is yours.

       -o [on|off]
              This  option  is much like -a.  It makes any open()
              of this device check to see that the device is  on-
              line  and  not  reporting any out of paper or other
              errors.  This is the correct setting for most  ver­
              sions of lpd.

       -C [on|off]
              This  option adds extra ("careful") error checking.
              When this option is on,  the  printer  driver  will
              ensure  that the printer is on-line and not report­
              ing any out of paper or other errors before sending

              that normally appear to  accept  data  when  turned
              off.

              NOTE:  This  option  is  obsolete  because it's the
              default in 2.1.131 kernel or later.

       -s     This option returns  the  current  printer  status,
              both as a decimal number from 0..255, and as a list
              of active flags.  When this option is specified, -q
              off, turning off the display of the current IRQ, is
              implied.

       -T [on|off]
              This option tell the lp driver to trust or not  the
              IRQ.  This option makes sense only if you are using
              interrupts.  If you tell the lp driver to trust the
              irq,  then,  when the lp driver will get an irq, it
              will send the next pending character to the printer
              unconditionally,  even  if the printer still claims
              to be BUSY.  This is  the  only  way  to  sleep  on
              interrupt (and so the handle the irq printing effi­
              ciently) at least on Epson Stylus  Color  Printers.
              The  lp  driver  automagically detects if you could
              get improved performance by setting this flag,  and
              in  such  case  it will warn you with a kernel mes­
              sage.

              NOTE: Trusting the irq is reported to  corrupt  the
              printing  on some hardware, you must try to know if
              your printer will work or not...

       -r     This option resets the port.  It requires  a  Linux
              kernel version of 1.1.80 or later.

       -q [on|off]
              This  option  sets printing the display of the cur­
              rent IRQ setting.


NOTES

       -o, -C, and -s all  require  a  Linux  kernel  version  of
       1.1.76 or later.

       -C requires a Linux version prior to 2.1.131.

       -T requires a Linux version of 2.1.131 or later.

       By  some  unfortunate  coincidence  the  ioctl LPSTRICT of
       2.0.36 has the same number as the ioctl LPTRUSTIRQ  intro­
       duced  in  2.1.131.  So,  use of the -T option on a 2.0.36
       kernel with an tunelp compiled under 2.1.131 or later  may
       have unexpected effects.


FILES

       /dev/lp?
       /proc/parport/*/*


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