tunelp
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 dic-
tated 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 printers. 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 report-
ing any out of paper or other errors. This is the correct set-
ting 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 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 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 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 ver-
sion 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)
