.\" $NetBSD: acpivga.4,v 1.3 2010/10/28 21:45:02 gsutre Exp $
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.Dd October 28, 2010
.Dt ACPIVGA 4
.Os
.Sh NAME
.Nm acpivga
.Nd ACPI Display Adapter and Output Devices
.Sh SYNOPSIS
.Cd "acpivga* at acpi?"
.Cd "acpiout* at acpivga?"
.Sh DESCRIPTION
The
.Nm
driver provides generic support for brightness control and output switching,
through
.Tn ACPI
video extensions.
The
.Tn ACPI
specification requires that systems containing a built-in display adapter
implement these extensions in their
.Tn ACPI
BIOS.
.Pp
The driver handles brightness hotkeys and display switch hotkeys.
In addition, the following
.Xr sysctl 8
read/write variables are provided (when hardware support is available):
.Bl -tag -width Ds
.It Va hw.acpi.acpivga0.bios_switch
BIOS output switching policy.
This boolean variable controls the behavior of the BIOS when a display
switch hotkey is pressed.
.Bl -tag -width xxx -compact
.It Sy 1
the BIOS should automatically switch outputs, with no interaction from
.Nm .
.It Sy 0
the BIOS should only notify
.Nm
of the desired output state changes.
.El
.It Va hw.acpi.acpiout0.brightness
Brightness level.
This integer variable typically ranges from 0 to 100, but any integer value
is accepted (the driver uses the closest brightness level supported by the
device).
.El
.Pp
Please note, however, that future versions of
.Nm
may remove these
.Xr sysctl 8
variables without prior notice.
.Sh SEE ALSO
.Xr acpi 4 ,
.Xr vga 4 ,
.Xr sysctl 8
.Rs
.%A Microsoft Corporation
.%D December 4, 2001
.%T Mobile System Displays and Windows
.%N Version 1.2c
.%U http://www.microsoft.com/whdc/archive/mobiledisplay.mspx
.Re
.Sh HISTORY
The
.Nm
driver appeared in
.Nx 6.0 .
.Sh AUTHORS
.An Gr\('egoire Sutre
.Aq gsutre@NetBSD.org
.Sh CAVEATS
The
.Nm
driver only supports PCI/PCI-X/PCI-E display adapters.
.Pp
Many
.Tn ACPI
BIOSes implement only part of the
.Tn ACPI
video extensions.
In particular, display output switching via these extensions often does not
work.
For this reason,
.Nm
enables
.Va hw.acpi.acpivga0.bios_switch
by default.
If the display switch hotkey does not work with this default setting, try
setting
.Va hw.acpi.acpivga0.bios_switch
to 0.
.Pp
Brightness level should be controlled via
.Xr wsconsctl 8
instead of
.Xr sysctl 8 .