table of contents
PPI(4) | Device Drivers Manual | PPI(4) |
NAME¶
ppi — user-space interface to ppbus parallel 'geek' portSYNOPSIS¶
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 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
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; 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. The headers required for user applications are not installed as part of the standard system.January 2, 1998 | Debian |