tunelp(8)						     Linux Programmer's Manual							 tunelp(8)

NAME

       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  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 <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 possible 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.

       -c <CHARS>
	      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 printers 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 print-
	      ers.  This may also make it possible 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 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 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 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 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  uncon-
	      ditionally,  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  per-
	      formance 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 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.

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)