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 user
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 typical dot matrix printers, polling will usually be enough. The default
is polling.
The following
ioctl(2) calls are supported:
-
int ioctl(int 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 influences only the polling driver.
-
int ioctl(int 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 influences only the polling driver.
-
int ioctl(int fd, LPABORT, int
arg)
- If arg is 0, the printer driver will retry on
errors, otherwise it will abort. The default is 0.
-
int ioctl(int 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.
-
int ioctl(int 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.
-
int ioctl(int 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.
-
int ioctl(int 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.
-
int ioctl(int fd, LPGETIRQ, int
*arg)
- Stores the currently used IRQ in arg.
-
int ioctl(int 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.
-
int ioctl(int fd, LPRESET)
- Resets the printer. No argument is used.
/dev/lp*
chmod(1),
chown(1),
mknod(1),
lpcntl(8),
tunelp(8)