Laptop backlight does not turn off

This seems a related problem (On a Toshiba):
http://bugme.osdl.org/show_bug.cgi?id=1944

I don't know how usefull it is, but here is my dmesg output regarding ACPI (note
that this laptop does not have APM)
ACPI: Looking for DSDT in initrd... not found!
ACPI: Subsystem revision 20050211
ACPI: Interpreter enabled
ACPI: Using IOAPIC for interrupt routing
ACPI: PCI Root Bridge [PCI0] (00:00)
ACPI: PCI Interrupt Routing Table [\_SB_.PCI0._PRT]
ACPI: Embedded Controller [EC0] (gpe 33)
ACPI: PCI Interrupt Routing Table [\_SB_.PCI0.P2P0._PRT]
ACPI: PCI Interrupt Routing Table [\_SB_.PCI0.AGP0._PRT]
ACPI: PCI Interrupt Link [LNK1] (IRQs 16 18 19) *0
ACPI: PCI Interrupt Link [LNK2] (IRQs 16 18 19) *0
ACPI: PCI Interrupt Link [LNK3] (IRQs 17) *0
ACPI: PCI Interrupt Link [LNK4] (IRQs 16 18 19) *0, disabled.
ACPI: PCI Interrupt Link [LNK5] (IRQs 16 18 19) *0
ACPI: PCI Interrupt Link [LSMB] (IRQs 20 21 22) *0
ACPI: PCI Interrupt Link [LUS0] (IRQs 20 21 22) *0
ACPI: PCI Interrupt Link [LUS1] (IRQs 20 21 22) *0
ACPI: PCI Interrupt Link [LUS2] (IRQs 20 21 22) *0
ACPI: PCI Interrupt Link [LMAC] (IRQs 20 21 22) *0, disabled.
ACPI: PCI Interrupt Link [LACI] (IRQs 20 21 22) *0
ACPI: PCI Interrupt Link [LMCI] (IRQs 20 21 22) *0
ACPI: PCI Interrupt Link [LPID] (IRQs 20 21 22) *0, disabled.
ACPI: PCI Interrupt Link [LTID] (IRQs 20 21 22) *0, disabled.
pnp: PnP ACPI init
pnp: PnP ACPI: found 12 devices
PnPBIOS: Disabled by ACPI PNP
PCI: Using ACPI for IRQ routing
ACPI: PCI Interrupt Link [LMCI] enabled at IRQ 22
ACPI: PCI interrupt 0000:00:06.1[B] -> GSI 22 (level, low) -> IRQ 22
ACPI wakeup devices:
ACPI: (supports S0 S3 S4 S5)
ACPI: CPU0 (power states: C1[C1] C2[C2])
ACPI: Thermal Zone [THRM] (50 C)
ACPI: PCI Interrupt Link [LNK5] enabled at IRQ 19
ACPI: PCI interrupt 0000:01:00.0[A] -> GSI 19 (level, low) -> IRQ 19
ACPI: PCI Interrupt Link [LNK3] enabled at IRQ 17
ACPI: PCI interrupt 0000:02:02.0[A] -> GSI 17 (level, low) -> IRQ 17
ACPI: PCI Interrupt Link [LUS0] enabled at IRQ 21
ACPI: PCI interrupt 0000:00:02.0[A] -> GSI 21 (level, low) -> IRQ 21
ACPI: PCI Interrupt Link [LUS1] enabled at IRQ 20
ACPI: PCI interrupt 0000:00:02.1[B] -> GSI 20 (level, low) -> IRQ 20
ACPI: PCI Interrupt Link [LUS2] enabled at IRQ 22
ACPI: PCI interrupt 0000:00:02.2[C] -> GSI 22 (level, low) -> IRQ 22
ACPI: PCI Interrupt Link [LACI] enabled at IRQ 21
ACPI: PCI interrupt 0000:00:06.0[A] -> GSI 21 (level, low) -> IRQ 21
ACPI: PCI Interrupt Link [LNK1] enabled at IRQ 18
ACPI: PCI interrupt 0000:02:00.0[A] -> GSI 18 (level, low) -> IRQ 18
ACPI: PCI Interrupt Link [LNK2] enabled at IRQ 16
ACPI: PCI interrupt 0000:02:01.0[A] -> GSI 16 (level, low) -> IRQ 16
ACPI: PCI interrupt 0000:02:04.0[A] -> GSI 18 (level, low) -> IRQ 18
ACPI: PCI interrupt 0000:02:04.1[B] -> GSI 16 (level, low) -> IRQ 16
ACPI: AC Adapter [ACAD] (on-line)
ACPI: Power Button (FF) [PWRF]
ACPI: Lid Switch [LID]
ibm_acpi: ec object not found
ACPI: Battery Slot [BAT1] (battery present)
ACPI: Video Device [VGA] (multi-head: yes rom: no post: no)

When does your screen fail to turn off? X doesn't use ACPI to attempt to blank
the screen.

Ping?

(In reply to comment #3)
> When does your screen fail to turn off? X doesn't use ACPI to attempt to blank
> the screen.

Sorry, didn't see the first reply.
I will try to see if it does console blanking (but I think it does not).

It fails to turn of on the Xscreensaver suspends, but also when doing xset dpms
commands (always blanks, but backlight stays on).

I need more sleep.

I had already tested it console only (by just waiting and by using setterm).
The display goes blank but the backlight never goes off.

If vbetool can't switch your screen off, then it sounds like you don't have a
DPMS BIOS. I'm not sure that we can do a great deal in that case.

(In reply to comment #7)
> If vbetool can't switch your screen off, then it sounds like you don't have a
> DPMS BIOS. I'm not sure that we can do a great deal in that case.

Can this be due to my laptop not having APM? (only ACPI).
I have read online that it works in Windows, but I have no idea how (nor can I
confirm this).

I will try with the Breezy LiveCD (without Nvidia drivers, which may also be a
factor).

Ok, I've done some testing

LiveCD with nv driver makes no difference
Breezy with newer Nvidia driver installed, no difference

I also had a reply to a thread I created on the zv5000 forums, this guy has the
reverse problem on a Gentoo box (backlight turns off, but screen does not).
http://www.r3000forums.com/viewtopic.php?t=1356

ACPI has greatly improved in Ubuntu 6.06 LTS. Could you please test whether the problem persists?

thanks

I have same kind of problem in Kubuntu Edgy.
Hardware: HP omnibook vt6200, ati mobility radeon. Video driver is ati (issue is also with vesa driver). Laptop backlight stays always on. Screen blanking only makes display black but backlight stays on.
If I switch backlight off with "xset dpms force off" backlight will stay off 30-60 seconds, then it will switch back on.
With "sudo radeontool light off" backlight stays off.

Same problem of yours with an hp nx7400 notebook (intel 945gma).
xset dpms off
shuts down the backlight for a few seconds.
Only vbetool dpms off shuts down backlight really.
I tried on debian etch (similar packages, same i810 driver, same notebook) the problem is not present.

It's a bug related to ubuntu's Xorg.
See also bug:
https://bugs.launchpad.net/distros/ubuntu/+source/xserver-xorg-video-i810/+bug/37364

Fixed in the Nvidia drivers that came with Edgy (HP ZV5174EA)

BTW, I changed my launchpad account a bit, I'm the original reporter

Changed state to fix released, given Guy's comment re this being fixed with Edgy drivers.

Unfortunately the latest Edgy updates as at today have not not fixed this for me. I'm running a Toshiba notebook with S3 Savage.

Running 'xset dpms force off' makes the screen go black but the backlight stays on (it doesn't even turn off for a second), and just a few seconds later the screen starts to increase in brightness and appears to 'display' the pattern of transistors making up the TFT panel itself.

I am happy for you to close this bug, and I'll go and lurk in the other similar backlight bugs until this is fixed, e.g.:

bug 71368
bug 37364
bug 37540
bug 41994
bug 40667
bug 30802

I encountred the same trouble with HP nc6400 laptop.
I was able to switch the backlight off with this command: sudo vbetool dpms standby