ACPI S3 suspend and LCD backlight

ACPI S3 suspend and LCD backlight

[yauh-acpi-CDzBh2wLF5MAvxtiuMwx3w]

Hi,

	It appears something in the ACPI suspend code turns on the
LCD backlight to print out the diagnostic messages. Is there any 
way to prevent this? Alternatively, is there a place in the drive
I can add a sequence to turn off the display just before it goes
to sleep?

System - Compaq TC1000 w/nVidia GeForce2 Go; Kernel is 2.6.13.4
User space is partially FC2 but has been largely updated through
self compiled binaries.

I have a patched X.org nv driver that supports dpms enough to
disable the backlight. I suspend the system with:

sleep 1; xset dpms force suspend 
sync
hwclock --systohc
echo 3 > /proc/acpi/sleep
hwclock --hctosys


The xset turns off the backlight but as soon as it gets to the echo 3 line,
the LCD comes on and displays the ACPI status messages. It then then 
proceeds to blank the screen but does NOT turn off the backlight.
If there is no way to disable the messages, I was hoping there is a
place I can hook into to twiddle the bit needed to disable the backlight.
Loading the video support module gives me an empty /proc/acpi/video directory.

Other then this backlight problem, everything else seems to work. 

This is where I originally found the patch for backlight DPMS on the
GeForce2Go -
http://www.mail-archive.com/devel-72qDnkntNoRAfugRpC6u6w@public.gmane.org/msg06145.html

P


Thanks.

-- Hunyue


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Re: ACPI S3 suspend and LCD backlight

[Matthew Garrett]

On Sat, Nov 12, 2005 at 10:39:04PM -0700, yauh-acpi-CDzBh2wLF5MAvxtiuMwx3w@public.gmane.org wrote:

> 	It appears something in the ACPI suspend code turns on the
> LCD backlight to print out the diagnostic messages. Is there any 
> way to prevent this? Alternatively, is there a place in the drive
> I can add a sequence to turn off the display just before it goes
> to sleep?

No, the ACPI suspend code doesn't do this (as far as I can tell). If you 
suspend from X, the kernel will switch away from X and X will restore 
the console state - which probably includes switching the backlight back 
on.

> The xset turns off the backlight but as soon as it gets to the echo 3 line,
> the LCD comes on and displays the ACPI status messages. It then then 
> proceeds to blank the screen but does NOT turn off the backlight.
> If there is no way to disable the messages, I was hoping there is a
> place I can hook into to twiddle the bit needed to disable the backlight.
> Loading the video support module gives me an empty /proc/acpi/video directory.

Try grabbing vbetool and do something like

FGCONSOLE=`fgconsole`
chvt 12
vbetool dpms off
echo -n 3 >/proc/acpi/sleep
chvt $FGCONSOLE

-- 
Matthew Garrett | mjg59-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org


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Re: ACPI S3 suspend and LCD backlight

[Pavel Machek]

Hi!

> > 	It appears something in the ACPI suspend code turns on the
> > LCD backlight to print out the diagnostic messages. Is there any 
> > way to prevent this? Alternatively, is there a place in the drive
> > I can add a sequence to turn off the display just before it goes
> > to sleep?
> 
> No, the ACPI suspend code doesn't do this (as far as I can tell). If you 
> suspend from X, the kernel will switch away from X and X will restore 
> the console state - which probably includes switching the backlight back 
> on.

ACPI does switch consoles, which may cause something like that... see
kernel/power/console.c .
								Pavel
-- 
Thanks, Sharp!


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