ASUS U46E laptop brightness

Sergiy Mikhailushko ooomka at
Sat Sep 28 12:37:03 UTC 2013

Hi all
Could you please help me with a little annoying problem concerning 
laptop backlight?
I've got ASUS U46E laptop running FreeBSD 9-STABLE amd64. The problem is 
that backlight is always set to maximum value. Pressing Fn+F5 
(brightness down) has no effect, just yielding the following to 

ACPI Error: Result stack is empty! State=0xfffffe00017fa800 
ACPI Exception: AE_AML_NO_RETURN_VALUE, Missing or null operand 
ACPI Exception: AE_AML_NO_RETURN_VALUE, While creating Arg 0 
ACPI Error: Method parse/execution failed [\_SB_.PCI0.GFX0.GCBL] (Node 
0xfffffe000181f600), AE_AML_NO_RETURN_VALUE (20110527/psparse-560)

What I've tried:

1) Flashed the latest BIOS version from ASUS website (ver301)

2) Upgraded OS to the latest STABLE version (last upgrade Aug 30 2013)

3) Loading acpi_asus module:
     # kldload acpi_asus
     # sysctl -a | grep asus

4) Loading acpi_video module:
    # sysctl 0 -> 0
     # sysctl 100 -> 60
     # sysctl 77 -> 60
     # sysctl 60 -> 60
Values are changed but brightness doesn't

5) Using acpi_call utility (not sure what value should be changed, tried 
acpi_call -p '\_SB_.PCI0.GFX0.GCBL' and acpi_call -p 
'\_SB_.PCI0.LPCB.EC0_._Q0E' -- both resulting in Unknown object type '0')

# uname -a
FreeBSD toysrv 9.2-PRERELEASE FreeBSD 9.2-PRERELEASE #2 r255810: Fri Sep 
27 14:27:49 EEST 2013     oomka at toysrv:/usr/obj/usr/src/sys/TOYSRV  amd64

# acpidump -dt > u46e.asl
[gzipped file attached]

I used to run i386 FreeBSD on this laptop -- the brightness control was 
okay on it. There were often kernel panics on that architecture so I've 
switched to amd64. Panics disappeared and the things work fine so far, 
except the screen brightness.
I know that my problem isn't critical when I'm working on daylight or 
with external LCD display, but when I have to work at the laptop at 
night -- this spotlight really drives me crazy. Thank you in advance for 
your help.

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