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.