NAME

lp − parallel printer interface

DESCRIPTION

The lp driver supports both the primary printer adapter (on the monochrome display adapter card) and secondary parallel printer adapters simultaneously.  Up to three printers are supported.  If an adapter for a printer is not installed, an attempt to open it will fail.  The close waits until all output is completed before returning to the user.  The lp driver allows only one process at a time to write to the adapter.  If it is already busy, an open for writing will return an error.  However, the driver allows multiple opens to occur if they are read-only. 

The parallel printer adapters are character devices.  The minor device number corresponds to the primary or secondary parallel printer adapter.  Thus, minor device 0 corresponds to the primary parallel printer adapter, while minor device 1 corresponds to the secondary adapter. 

The line printer driver allows users to determine how often the system will check whether a printer job is done and how often the system will send a message to the console alerting the operator that a printer needs attention.  The two tunable parameters are:

where the system parameter HZ (hertz) is the number of ticks per second of the system clock (100). 

This enhancement improves performance when using certain monochrome adapter ports.  Some parallel port interfaces, such as the parallel port on many monochrome display adapters, do not latch (retain) their interrupt signals.  This results in a loss of expected completion (READY) interrupts.  To prevent this loss from slowing or stopping printer output, common code shared by the lp and slp drivers now uses a timeout mechanism to poll the interfaces for completion.  LP_POLLINT (default 1/20th of a second) defines this polling interval. 

When the printer driver detects a condition requiring operator intervention (such as paper-out), it writes a message on the console.  LP_WARNINT (default 2 minutes) defines (in minutes) the interval between these warnings. 

These parameters may be added to your system using kconfig. Select the Configure menu, then select Tunables −> Parameters −> Device Driver, then arrow to the specific tunable (LP_POLLINT or LP_WARNINT).  The system will prompt you for the parameter name and its value. 

FILES

/dev/lp*

SEE ALSO

kconfig(1). 
INTERACTIVE UNIX System Installation and Maintenance Guide.

ADDED VALUE

This entry, supplied by SunSoft, Inc., contains enhancements to UNIX ­System V. 

\*U  —  Version 1.0