tunelp(8)		   Linux Programmers Manual		    tunelp(8)



NAME
       tunelp - set various parameters for the lp device

SYNOPSIS
       tunelp    [-i    | -t  | -c  | -w  | -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 wont  work
       without	it...)	 Without  parameters,  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 follows:


       -i 
	      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 print
	      ing 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 
	      is the amount of time in jiffies that the driver	waits  if  the
	      printer  doesnt  take  a character for the number of tries dic
	      tated by the -c parameter.  10 is the  default  value.   If  you
	      want  fastest  possible  printing,  and  dont care about system
	      load, you may set this to 0.  If you dont 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.


       -c 
	      is  the  number  of  times  to  try to output a character to the
	      printer before sleeping for -t .   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
	      printers that become jerky otherwise, but you must set  this  to
	      1 to handle the maximal CPU efficiency if you are using inter
	      rupts. 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  to 0 is equivalent to setting  -c    to
	      infinity.


       -w 
	      is the number of usec we wait while playing with the strobe sig
	      nal.  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 possible to use
	      longer cables. Its 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 computer, 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 arent,  you	might  rather
	      that your printer spooler find out that the printer isnt 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 versions 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  reporting  any  out  of paper or other errors
	      before sending data.  This is particularly useful  for  printers
	      that normally appear to accept data when turned off.

	      NOTE:  This  option  is  obsolete  because  its  the default in
	      2.1.131 kernel or later.


       -s     This option returns the current printer status, both as a  deci
	      mal  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  is	obsolete.  It  was added in Linux 2.1.131, and
	      removed again in Linux 2.3.10. The below is for these  old  ker
	      nels only.

	      This  option  tells 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 efficiently) 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 message.

	      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 current IRQ set
	      ting.



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.


BUGS
       By some unfortunate coincidence the ioctl LPSTRICT of  2.0.36  has  the
       same  number  as the ioctl LPTRUSTIRQ introduced 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/*/*



tunelp				  7 May 1999			     tunelp(8)