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 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 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 is obsolete. It was added in Linux 2.1.131, and
removed again in Linux 2.3.10. The below is for these old
kernels 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
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/*/*
AVAILABILITY
The tunelp command is part of the util-linux-ng package and is
available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.