NAME¶

ppi — user-space interface to ppbus parallel 'geek' port

SYNOPSIS¶

device ppi

Minor numbering: unit numbers correspond directly to ppbus numbers.

#include <dev/ppbus/ppi.h>
#include <dev/ppbus/ppbconf.h>

DESCRIPTION¶

The ppi driver provides a convenient means for user applications to manipulate the state of the parallel port, enabling easy low-speed I/O operations without the security problems inherent with the use of the /dev/io interface.

PROGRAMMING INTERFACE¶

All I/O on the ppi interface is performed using ioctl() calls. Each command takes a single uint8_t argument, transferring one byte of data. The following commands are available:

PPIGDATA, PPISDATA

Get and set the contents of the data register.

PPIGSTATUS, PPISSTATUS

Get and set the contents of the status register.

PPIGCTRL, PPISCTRL

Get and set the contents of the control register. The following defines correspond to bits in this register. Setting a bit in the control register drives the corresponding output low.

STROBE

 

AUTOFEED

 

nINIT

 

SELECTIN

 

PCD

 

PPIGEPP, PPISEPP

Get and set the contents of the EPP control register.

PPIGECR, PPISECR

Get and set the contents of the ECP control register.

PPIGFIFO, PPISFIFO

Read and write the ECP FIFO (8-bit operations only).

EXAMPLES¶

To present the value 0x5a to the data port, drive STROBE low and then high again, the following code fragment can be used:

	int		fd;
	uint8_t		val;

	val = 0x5a;
	ioctl(fd, PPISDATA, &val);
	ioctl(fd, PPIGCTRL, &val);
	val |= STROBE;
	ioctl(fd, PPISCTRL, &val);
	val &= ~STROBE;
	ioctl(fd, PPISCTRL, &val);

BUGS¶

The inverse sense of signals is confusing.

The ioctl() interface is slow, and there is no way (yet) to chain multiple operations together.

The headers required for user applications are not installed as part of the standard system.