.\" Copyright (c) 1997
.\"      Michael Smith
.\"
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.\" $FreeBSD: src/share/man/man4/ppi.4,v 1.4.2.7 2001/12/17 11:30:12 ru Exp $
.\" $DragonFly: src/share/man/man4/ppi.4,v 1.4 2007/12/15 10:33:38 swildner Exp $
.\"
.Dd January 2, 1998
.Dt PPI 4
.Os
.Sh NAME
.Nm ppi
.Nd "user-space interface to ppbus parallel 'geek' port"
.Sh SYNOPSIS
.Cd "device ppi"
.Pp
Minor numbering:  Unit numbers correspond directly to ppbus numbers.
.Sh DESCRIPTION
The
.Nm
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
.Pa /dev/io
interface.
.Sh PROGRAMMING INTERFACE
.In dev/misc/ppi/ppi.h
.In bus/ppbus/ppbconf.h
.Pp
All I/O on the
.Nm
interface is performed using
.Fn ioctl
calls.  Each command takes a single
.Ft u_int8_t
argument, transferring one byte of data.  The following commands are
available:
.Bl -tag -width indent
.It Dv PPIGDATA , PPISDATA
Get and set the contents of the data register.
.It Dv PPIGSTATUS , PPISSTATUS
Get and set the contents of the status register.
.It Dv 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.
.Bl -tag -width indent -compact
.It Dv STROBE
.It Dv AUTOFEED
.It Dv nINIT
.It Dv SELECTIN
.It Dv PCD
.El
.It Dv PPIGEPPA , PPISEPPA
Get and set the address bits of the EPP control register.
.It Dv PPIGEPPD , PPISEPPD
Get and set the data bits of the EPP control register.
.It Dv PPIGECR , PPISECR
Get and set the contents of the ECP control register.
.It Dv PPIGFIFO , PPISFIFO
Read and write the ECP FIFO (8-bit operations only).
.El
.Sh EXAMPLES
To present the value 0x5a to the data port, drive STROBE low and then high
again, the following code fragment can be used:
.Bd -literal -compact

	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);

.Ed
.Sh BUGS
The inverse sense of signals is confusing.
.Pp
The
.Fn ioctl
interface is slow, and there is no way (yet) to chain multiple operations together.