.\" $NetBSD: joy.4,v 1.9 2010/03/22 18:58:31 joerg Exp $
.\"
.\" Copyright (c) 1996 Matthieu Herrb
.\" All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
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.\"    notice, this list of conditions and the following disclaimer.
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.\"    notice, this list of conditions and the following disclaimer in the
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.\"    must display the following acknowledgement:
.\"      This product includes software developed by Christopher G. Demetriou.
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.\"    derived from this software without specific prior written permission
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.Dd July 22, 2006
.Dt JOY 4
.Os
.Sh NAME
.Nm joy
.Nd game adapter driver
.Sh SYNOPSIS
.Cd "joy* at acpi?"
.Cd "joy* at eap?"
.Cd "joy* at eso?"
.Cd "joy0 at isa? port 0x201"
.Cd "joy* at isapnp?"
.Cd "joy* at ofisa?"
.Cd "joy* at pci?"
.Cd "joy* at pnpbios? index ?"
.Sh DESCRIPTION
This driver provides access to the game adapter.
The lower bit in the minor device number selects the joystick: 0
is the first joystick and 1 is the second.
.Pp
The game control adapter allows up to two joysticks to be attached to
the system.
The adapter plus the driver convert the present resistive value to
a relative joystick position.
On receipt of an output signal, four timing circuits are started.
By determining the time required for the circuit to time-out (a
function of the resistance), the paddle position can be determined.
The adapter could be used as a general purpose I/O card with four
analog (resistive) inputs plus four digital input points.
.Pp
Applications may call
.Xr ioctl 2
on a game adapter driver file descriptor
to set and get the offsets of the two potentiometers and the maximum
time-out value for the circuit.
The
.Xr ioctl 2
commands are listed in
.In machine/joystick.h
and currently are:
.Pp
.Bl -tag -width JOY_GET_X_OFFSET -compact
.It Dv JOY_SETTIMEOUT
Sets the maximum time-out for the adapter.
.It Dv JOY_GETTIMEOUT
Returns the current maximum time-out.
.It Dv JOY_SET_X_OFFSET
Sets an offset on X value.
.It Dv JOY_GET_X_OFFSET
Returns the current X offset.
.It Dv JOY_SET_Y_OFFSET
Sets an offset on Y value.
.It Dv JOY_GET_Y_OFFSET
Returns the current Y offset.
.El
.Pp
All these commands take an integer parameter.
.Pp
.Xr read 2
on the file descriptor returns a
.Fa joystick
structure:
.Bd -literal -offset indent
struct joystick {
	int x;
	int y;
	int b1;
	int b2;
};
.Ed
.Pp
The fields have the following functions:
.Bl -tag -width xxx
.It Fa x
current X coordinate of the joystick (or position of paddle 1)
.It Fa y
current Y coordinate of the joystick (or position of paddle 2)
.It Fa b1
current state of button 1
.It Fa b2
current state of button 2
.El
.Pp
The b1 and b2 fields in struct joystick are set to 1 if the
corresponding button is down, 0 otherwise.
.Pp
The x and y coordinates are supposed to be between 0 and 255 for a
good joystick and a good adapter.
Unfortunately, because of the
hardware hack that is used to measure the position (by measuring the
time needed to discharge an RC circuit made from the joystick's
potentiometer and a capacitor on the adapter), calibration
is needed to determine exactly what values are returned for a specific
joystick/adapter combination.
Incorrect hardware can yield negative or values greater than 255.
.Pp
A typical calibration procedure uses the values returned at lower
left, center and upper right positions of the joystick to compute the
relative position.
.Pp
This calibration is not part of the driver.
.Sh FILES
.Bl -tag -width Pa -compact
.It Pa /dev/joy0
first joystick
.It Pa /dev/joy1
second joystick
.El
.Sh SEE ALSO
.Xr acpi 4 ,
.Xr eap 4 ,
.Xr eso 4 ,
.Xr isa 4 ,
.Xr isapnp 4 ,
.Xr ofisa 4 ,
.Xr pci 4 ,
.Xr pnpbios 4
.Sh AUTHORS
Jean-Marc Zucconi wrote the
.Fx
driver.
Matthieu Herrb ported it to
.Nx
and wrote this manual page.