lp — line printer devices
#include <linux/lp.h>
lp
[0–2]
are character devices for the parallel line printers; they
have major number 6 and minor number 0–2. The minor
numbers correspond to the printer port base addresses 0x03bc,
0x0378 and 0x0278. Usually they have mode 220 and are owned
by root and group lp. You can use printer ports either with
polling or with interrupts. Interrupts are recommended when
high traffic is expected, for example, for laser printers.
For usual dot matrix printers polling will usually be enough.
The default is polling.
The following ioctl(2) calls are supported:
fd
, LPTIME, int arg
)
Sets the amount of time that the driver sleeps
before rechecking the printer when the printer's buffer
appears to be filled to arg
. If you have a fast
printer, decrease this number; if you have a slow
printer then increase it. This is in hundredths of a
second, the default 2 being 0.02 seconds. It only
influences the polling driver.
fd
, LPCHAR, int arg
)
Sets the maximum number of busy-wait iterations
which the polling driver does while waiting for the
printer to get ready for receiving a character to
arg
. If
printing is too slow, increase this number; if the
system gets too slow, decrease this number. The default
is 1000. It only influences the polling driver.
fd
, LPABORT, int arg
)
If arg
is
0, the printer driver will retry on errors, otherwise
it will abort. The default is 0.
fd
, LPABORTOPEN, int arg
)
If arg
is
0, open(2) will be
aborted on error, otherwise error will be ignored. The
default is to ignore it.
fd
, LPCAREFUL, int arg
)
If arg
is
0, then the out-of-paper, offline and error signals are
required to be false on all writes, otherwise they are
ignored. The default is to ignore them.
fd
, LPWAIT, int arg
)
Sets the number of busy waiting iterations to wait
before strobing the printer to accept a just-written
character, and the number of iterations to wait before
turning the strobe off again, to arg
. The specification
says this time should be 0.5 microseconds, but
experience has shown the delay caused by the code is
already enough. For that reason, the default value is
0. This is used for both the polling and the interrupt
driver.
fd
, LPSETIRQ, int arg
)
This ioctl(2) requires
superuser privileges. It takes an int containing the
new IRQ as argument. As a side effect, the printer will
be reset. When arg
is 0, the polling
driver will be used, which is also default.
fd
, LPGETIRQ, int *arg
)
Stores the currently used IRQ in arg
.
fd
, LPGETSTATUS, int *arg
)
Stores the value of the status port in arg
. The bits have the
following meaning:
LP_PBUSY | inverted busy input, active high |
LP_PACK | unchanged acknowledge input, active low |
LP_POUTPA | unchanged out-of-paper input, active high |
LP_PSELECD | unchanged selected input, active high |
LP_PERRORP | unchanged error input, active low |
Refer to your printer manual for the meaning of the signals. Note that undocumented bits may also be set, depending on your printer.
fd
, LPRESET)Resets the printer. No argument is used.
chmod(1), chown(1), mknod(1), lpcntl(8), tunelp(8)
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