Intermediate levels of brightness

Asked by Pedro Izecksohn on 2012-08-31

After the last upgrade, I'm unable to set an intermediate level of brightness: the level of brightness is being pushed to its maximum or to its minimum. It happens when I press Fn+Up or Fn+Down and it also happens inside the Brightness and Lock window: The level indicator passes through all the levels, changing the brightness at every step, but it does not stop at each level of brightness. I used to use an intermediate level of brightness until some hours ago on this same installation.

I use Ubuntu version 12.04.1 LTS on a Intel(R) Core(TM) i5-2410M CPU with a VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) and a 3D controller: NVIDIA Corporation GF108 [GeForce GT 540M] (rev a1).

What should I do to fix this?

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Ubuntu acpi Edit question
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N1ck 7h0m4d4k15 (nicktux) said : #1

Hi ,
as you correct , mention the affected package (acpi) maybe is a good idea to try a workaround for this problem.

I will tell you one.

Open a terminal (ctrl+alt+t) and apply this command
gksudo gedit /etc/default/grub

at the opened window , find the line : GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
and change it. Make it like this :GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"
save the document and then in terminal run
sudo update-grub

reboot your PC .


N1ck 7h0m4d4k15 (nicktux) said : #2

Because the line braked i will give you again the line as should be after the change.
You must change the line to look like this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"


What is the make and model of the system?

Dual GPU systems are a massive headache in Linux. I expect you will have a tonne of issues with this outside of Windows.

Pedro Izecksohn (izecksohn) said : #4

The solution
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"
fixed the Brightness and Lock window scrollbar, but it did not fix the Fn+Up or Fn+Down problem, only changed it: Now the level indicator may be set only to the maximum brightness or to one step below it.

Pedro Izecksohn (izecksohn) said : #5

The Brightness and Lock window scrollbar is working fine.
The Fn+Up or Fn+Down brightness indicator is not working properly.

What is the make and model of the system?


N1ck 7h0m4d4k15 (nicktux) said : #7

You can remove the parameter "acpI_backlight=vendor" the same way we added . Do not forget , at the end to run
sudo update-grub
for the changes to take effect.

Another good parameter , as we did above , might be acpi_osi=
line should be: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi="

Because you have 2 GPUs , do you use the bumblebee project or you have been disabled the integrated Intel GPU ?

Bumblebee project is here , take a look :

If this is an ACPI problem then you can test it with the latest Kernel . Latest kernel included in Ubuntu 12.10 (Unstable) .
You can download ubuntu 12.10 Daily-Build from here :
Do not install 12.10 , just run it as a live Usb / CD and test if keys work there.


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