.\"	$OpenBSD: xf86.4,v 1.12 2000/12/17 21:10:31 matthieu Exp $
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.\" Copyright (c) 1998 Matthieu Herrb
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.Dd February 20, 1998
.Dt XF86 4 i386
.Os
.Sh NAME
.Nm xf86
.Nd
XFree86 aperture driver
.Sh SYNOPSIS
.Cd "option APERTURE"
.Sh DESCRIPTION
The
.Pa /dev/xf86
driver provides access to the memory and I/O ports of a VGA board for
use by the XFree86 X servers
when running with a kernel security level > 0.
.Pp
The X servers require the use of this driver.
.Sh ACCESS CONTROL
Access to the
.Pa /dev/xf86
device is allowed when the sysctl variable
.Va machdep.allowaperture
>= 1.
This variable (which default value is 0)
can only be manipulated when the security level is <= 0, so it should be
set in
.Pa /etc/sysctl.conf .
The possible values for 
.Va machdep.allowaperture 
are:
.Bl -tag -width Ds
.It 0
the aperture driver is disabled. Opening it returns
.Dv EPERM. 
.It 1
the aperture driver allows access to standard VGA framebuffer and
BIOS.
.It 2
the aperture driver allow access to the whole 1st megabyte of physical
memory, for the use of the int10 emulation in XFree86 4.0.x. 
Note that this can cause some security problems, since the process that has
access to the aperture driver can also access part of the kernel
memory. 
.El
.Sh SEE ALSO
.Xr XF86_Accel 1 ,
.Xr XF86_SVGA 1 ,
.Xr options 4 ,
.Xr sysctl.conf 5 ,
.Xr config 8 ,
.Xr sysctl 8
.Sh HISTORY
.Pa /dev/xf86
was introduced as a loadable kernel module for NetBSD 0.9C
with XFree86 3.1.
It was integrated as an in-kernel device on
.Ox 2.3 .
It is required in order to allow access to I/O ports for all X servers since
.Ox 2.4 .
.Sh AUTHORS
The aperture driver was written by Matthieu Herrb.
.Sh BUGS
This driver allows access to all addresses above
.Va physmem .
It should be restricted to the actual address range of the video
memory.