Dell Inspiron 8100 - how to turn off LCD backlight (in console mode)?

I have an old laptop, Dell Inspiron 8100.
It runs FreeBSD, RELENG_6:
root@kg-i82# uname -a
FreeBSD kg-i82.kg4.no 6.3-PRERELEASE FreeBSD 6.3-PRERELEASE #2: Sat Oct 27 02:42:35 CEST 2007 root@xxxxxxxxxxxxx:/usr/obj/usr/src/sys/I81K i386

The machine has a Nvidia gfx card:
root@kg-i82# pciconf -lv | grep -B 4 VGA
acpi_video0@pci1:0:0: class=0x030000 card=0x00e61028 chip=0x011210de rev=0xb2 hdr=0x00
vendor = 'NVIDIA Corporation'
device = 'NV11 GeForce2 Go / MX Ultra'
class = display
subclass = VGA

It is used as a firewall, so it doesn't run Xorg, it only runs in console (text) mode.
I use blank_saver to turn off the screen (text), and this works. I have tested with green_saver as well, and that also works.

The problem is that the LCD backlight stays on. How do I turn it off?
Ideally, the backlight would turn off with the screensaver, and turn on when the screensaver is deactivated again.

I tried with acpi_video, which gives me this:
root@kg-i82# sysctl hw.acpi.video
hw.acpi.video.crt0.active: 0
hw.acpi.video.lcd0.active: 1

I can change hw.acpi.video.lcd0.active to 0 (zero), but the display still stays on.
It doesn't seem like the i8k have a lid switch either:
root@kg-i82# sysctl hw.acpi
hw.acpi.supported_sleep_state: S1 S3 S4 S5
hw.acpi.power_button_state: S5
hw.acpi.sleep_button_state: S1
hw.acpi.lid_switch_state: NONE
hw.acpi.standby_state: S1
hw.acpi.suspend_state: S3
hw.acpi.sleep_delay: 1
hw.acpi.s4bios: 1
hw.acpi.verbose: 0
hw.acpi.disable_on_reboot: 0
hw.acpi.handle_reboot: 0
hw.acpi.reset_video: 0
hw.acpi.cpu.cx_lowest: C1
hw.acpi.acline: 1
hw.acpi.battery.life: 91
hw.acpi.battery.time: -1
hw.acpi.battery.state: 2
hw.acpi.battery.units: 2
hw.acpi.battery.info_expire: 5
hw.acpi.thermal.min_runtime: 0
hw.acpi.thermal.polling_rate: 10
hw.acpi.thermal.user_override: 0
hw.acpi.thermal.tz0.temperature: 60.5C
hw.acpi.thermal.tz0.active: -1
hw.acpi.thermal.tz0.passive_cooling: 0
hw.acpi.thermal.tz0.thermal_flags: 0
hw.acpi.thermal.tz0._PSV: -1
hw.acpi.thermal.tz0._HOT: -1
hw.acpi.thermal.tz0._CRT: 101.0C
hw.acpi.thermal.tz0._ACx: -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
hw.acpi.video.crt0.active: 0
hw.acpi.video.lcd0.active: 1

There isn't an acpi_dell or acpi_i8k module, at least I haven't found one.
I have searched quite a bit on Google, but haven't found anything helpful.

Any hints on how to get the backlight to turn off and on again (synced to the console screensaver)?
--
Torfinn Ingolfsen,
Norway
.