API to turn off the display

Stijn Hoop stijn at win.tue.nl
Wed Jan 28 14:23:31 PST 2004

On Thu, Jan 29, 2004 at 06:07:27AM +0900, Taku YAMAMOTO wrote:
> I wrote a driver that handles what John told.
> http://access.cent.saitama-u.ac.jp/~taku/freebsd/acpi_vid-20031013.tar.gz
> MD5 (acpi_vid-20031013.tar.gz) = adbfa6931e505544fb784e00c7b974e7
> This driver uses ACPI video extension to control display switching and
> backlight brightness. So working ACPI is a requisition for this driver.
> Whether it does or does not work depends heavily on how well the BIOS written,
> however, I hope it worth trying.
> Suggestions, working/not-working reports etc are very appreciated.

I can compile & kldload this module just fine on a -CURRENT from this morning,
on a Dell D600 laptop.

Output from 'sysctl hw.acpi.video' after loading the module:

hw.acpi.video.crt0.active: 0
hw.acpi.video.lcd0.active: 0
hw.acpi.video.out0.active: 0

Which is not entirely correct because the LCD is certainly on & working :)
This also is the initial state after a reboot or shutdown.

When switching to sleep state S1 (by closing the lid) the display is not
turned off automatically. However, I can switch off the LCD manually by doing

# sysctl hw.acpi.video.lcd0.active=1
# sysctl hw.acpi.video.lcd0.active=0

and I can subsequently restore it by (blindly) typing

# sysctl hw.acpi.video.lcd0.active=1

Furthermore, when booted with an external monitor connected (but only then),
the crt0 part also seems to work. And even although the laptop's shortcut key
for switching between LCD / CRT seems to disallow having both screens on at
the same time, I can make that work by toggling the apropriate sysctls, so it
definitely appears to work! Unfortunately, I cannot test out0 right now.

Thank you for this driver, I hope this report is of help.


The very powerful and the very stupid have one thing in common.  Instead of
altering their views to fit the facts, they alter the facts to fit their views
... which can be very uncomfortable if you happen to be one of the facts that
needs altering.
		-- Doctor Who, "Face of Evil"
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