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.\" Copyright (c) 2004 Mark Santcroos <marks@ripe.net>
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.Dd November 8, 2004
.Dt ACPI_VIDEO 4
.Os
.Sh NAME
.Nm acpi_video
.Nd ACPI Video Extensions driver
.Sh SYNOPSIS
.Cd "device acpi_video"
.Sh DESCRIPTION
This driver uses the ACPI Video Extensions to control display switching and
backlight brightness.
The availability of the
.Xr sysctl 8
variables depends on the functions offered by the host's ACPI implementation.
.Sh SYSCTL VARIABLES
The following sysctls are currently implemented,
where
.Aq Ar device
is
.Va crt , lcd ,
or
.Va tv :
.Bl -tag -width indent
.It Va hw.acpi.video. Ns Ao Ar device Ac Ns Va .active
Current state of the output device.
.It Va hw.acpi.video. Ns Ao Ar device Ac Ns Va .levels
List of supported brightness levels.
.It Va hw.acpi.video. Ns Ao Ar device Ac Ns Va .brightness
Current brightness level of the device.
.It Va hw.acpi.video. Ns Ao Ar device Ac Ns Va .fullpower
Preset brightness level to be used in full power mode.
.It Va hw.acpi.video. Ns Ao Ar device Ac Ns Va .economy
Preset brightness level to be used in economy mode.
.El
.Pp
Defaults for these variables can be set in
.Xr sysctl.conf 5 ,
which is parsed at boot-time.
.Sh COMPATIBILITY
In order for
.Nm
to attach correctly,
.Nm
should be loaded after any of the DRM kernel modules.
This can be achieved by setting the correct order in
.Xr rc.conf 5
using the kld_list directive.
.Sh SEE ALSO
.Xr acpi 4 ,
.Xr loader.conf 5 ,
.Xr sysctl.conf 5 ,
.Xr sysctl 8
.Sh HISTORY
The
.Nm
driver first appeared in
.Fx 5.3 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written by
.An Taku YAMAMOTO Aq Mt taku@cent.saitama-u.ac.jp .
This manual page was written by
.An Mark Santcroos Aq Mt marks@ripe.net .
.Sh BUGS
Some systems only perform output switching via SMM even though they export
the proper information via ACPI.
On such systems, the proper hotkeys or OEM driver (for example,
.Xr acpi_toshiba 4 )
must be used instead.