PPI(4)

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

SYNOPSIS
device ppi

Minor numbering: Unit numbers correspond directly to ppbus numbers.

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
<dev/misc/ppi/ppi.h> <bus/ppbus/ppbconf.h>

All I/O on the ppi interface is performed using ioctl() calls. Each command takes a single u_int8_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

PPIGEPPA, PPISEPPA
    Get and set the address bits of the EPP control register.

PPIGEPPD, PPISEPPD
    Get and set the data bits 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;
    	u_int8_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.