1.\" Copyright (c) 2000-2002 2.\" Diomidis D. Spinellis, Athens, Greece 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer as 10.\" the first lines of this file unmodified. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY Diomidis D. Spinellis ``AS IS'' AND ANY 16.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 18.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL Diomidis D. Spinellis BE 19.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 20.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 21.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 22.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 23.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 24.\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 25.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26.\" 27.\" $FreeBSD$ 28.\" 29.Dd January 14, 2005 30.Dt PBIO 4 i386 31.Os 32.Sh NAME 33.Nm pbio 34.Nd 8255 parallel peripheral interface basic 35.Tn I/O 36driver 37.Sh SYNOPSIS 38.Cd "device pbio" 39.Pp 40In 41.Pa /boot/device.hints : 42.Cd hint.pbio.0.at="isa" 43.Cd hint.pbio.0.port="0x360" 44.Pp 45.In dev/pbio/pbioio.h 46.Sh DESCRIPTION 47The 48.Nm 49driver supports direct access to the Intel 8255A programmable 50peripheral interface (PPI) chip running in mode 0 (simple 51.Tn I/O ) . 52Such an interface provides 24 digital 53.Tn I/O 54lines. 55The driver is designed for performing 56.Tn I/O 57under program control using 58peripherals such as the 59.Tn Advantech 60.Tn PCL-724 61card, which emulates the Intel 8255A PPI in mode 0. 62Other 8255A-based peripherals such as the 63.Tn BMC 64Messsysteme 65.Tn PIO24II 66card have also been reported to work. 67.Pp 68The PPI provides two 8-bit ports (port A and port B) and 69two 4-bit ports (port C upper, port C lower). 70Each port can be individually programmed for input and 71(latched) output, 72and appears at a different offset of the device's base 73.Tn I/O 74address. 75.Pp 76A separate register allows the configuration of ports for input 77or output. 78The device is so simple, that reliably probing for it when 79input data arrives at its terminals is impossible; 80therefore the kernel configuration has to specify the 81device's base address. 82The device driver provides four character devices that 83correspond to the peripheral's 84.Tn I/O 85ports. 86Opening a device for read or write automatically configures 87the corresponding hardware port for input or output. 88At boot time all ports are set configured for input to avoid damaging 89external circuitry. 90.Pp 91A set of 92.Xr ioctl 2 93requests allow polled input and paced output to be 94efficiently performed at the driver level without expensive 95user/kernel context switching. 96The driver can perform 97.Tn I/O 98in three different ways: 99.Bl -tag -width ".No Differential" 100.It Basic 101The read or write operation returns immediately after reading 102or writing the data to the port at bus speed. 103.It Paced 104Data is transferred from or to the port at intervals specified 105by a separate 106.Xr ioctl 2 107call. 108.It Differential 109(Input only.) 110Only port values that differ from the previous port value are returned. 111.El 112.Pp 113The pacing interval is specified in 114.Em Hz 115unit increments. 116Setting a pace of 117.Ar n 118seconds 119will result in no more than one value being read or written every 120.Ar n 121seconds. 122Single byte read/write operations will take at least 123.Ar n 124seconds to complete. 125.Pp 126The following 127.Xr ioctl 2 128calls are supported: 129.Bl -tag -width ".Dv PBIO_SETIPACE" 130.It Dv PBIO_SETDIFF 131accepts a pointer to an integer as the third argument, 132and sets the driver for differential input if the integer is non-zero. 133The input pace speed determines the periodic interval the driver will use to 134examine the port for a changed value. 135.It Dv PBIO_GETDIFF 136accepts a pointer to an integer as the third argument, 137and sets the integer to the last set value for differential input. 138.It Dv PBIO_SETIPACE 139accepts a pointer to an integer as the third argument, 140and sets the driver's input pacing speed to the value of that integer. 141.It Dv PBIO_GETIPACE 142accepts a pointer to an integer as the third argument, 143and sets the integer to the last set value for the input pace. 144.It Dv PBIO_SETOPACE 145accepts a pointer to an integer as the third argument, 146and sets the driver's output pacing speed to the value of that integer. 147.It Dv PBIO_GETOPACE 148accepts a pointer to an integer as the third argument, 149and sets the integer to the last set value for the output pace. 150.El 151.Sh FILES 152.Bl -tag -width ".Pa /dev/pbio0ch" -compact 153.It Pa /dev/pbio0a 154Port A (8 bit 155.Tn I/O ) . 156.It Pa /dev/pbio0b 157Port B (8 bit 158.Tn I/O ) . 159.It Pa /dev/pbio0ch 160Port C upper (4 bit 161.Tn I/O ) . 162.It Pa /dev/pbio0cl 163Port C lower (4 bit 164.Tn I/O ) . 165.El 166.Sh SEE ALSO 167.Rs 168.%A "Diomidis Spinellis" 169.%T "The information furnace: Consolidated home control" 170.%D "2003" 171.%J "Personal and Ubiquitous Computing" 172.%N 1 173.%V 7 174.%P "53-69" 175.Re 176.Sh HISTORY 177The 178.Nm 179device was first used under 180.Fx 4.1 . 181.Sh AUTHORS 182.An "Diomidis D. Spinellis" Aq dds@aueb.gr 183.Sh BUGS 184One of the 185.Tn PCL-724 186card's inputs can optionally be wired to generate an interrupt. 187This feature is not supported. 188