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
Theppi 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.
STROBEAUTOFEEDnINITSELECTINPCD
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.