XF86(4)               OpenBSD Programmer's Manual (i386)               XF86(4)

NAME
     xf86 - XFree86 aperture driver

SYNOPSIS
     option APERTURE

DESCRIPTION
     The /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 securi-
     ty level > 0.

     The X servers require the use of this driver.

ACCESS CONTROL
     Access to the /dev/xf86 device is allowed when the sysctl variable
     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 /etc/sysctl.conf. The possible values for machdep.allowaperture are:

     0       the aperture driver is disabled.  Opening it returns EPERM.

     1       the aperture driver allows access to standard VGA framebuffer and
             BIOS.

     2       the aperture driver allows access to the whole 1st megabyte of
             physical memory, permitting 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 ac-
             cess part of the kernel memory.

SEE ALSO
     XF86_Accel(1), XF86_SVGA(1), options(4), sysctl.conf(5), config(8),
     sysctl(8)

HISTORY
     /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 OpenBSD 2.3.
     It is required in order to allow access to I/O ports for all X servers
     since OpenBSD 2.4.

AUTHORS
     The aperture driver was written by Matthieu Herrb.

BUGS
     This driver allows access to all addresses above physmem. It should be
     restricted to the actual address range of the video memory.

OpenBSD 3.0                    February 20, 1998                             1
