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#1 2014-12-12 15:13:01

starflower
Member
From: UK
Registered: 2014-12-12
Posts: 3

[Solved] Having problems gettting Brightness Control to work on Mint 17 Xfce

Hi,

I have a new install of Mint 17 Xfce on an Acer Travelmate B115-M notebook.
In short the brightness control does not work. There is a GUI slider bar that lengthens/shortens in response to pushing the Fn + Brightness keys but the brightness wont change.

I've had this issue before on an ACER laptop and it was easilly fixed by editing the /etc/default/grub file with a line containing "acpi_backlight=vendor". However, this no longer seems to work with Mint 17.

I have also tried the approach of editing the /usr/share/X11/xorg.conf.d/20-intel.conf file as described in:
http://forums.linuxmint.com/viewtopic.php?f=42&t=179880    This doesnt work either although it seems to for a lot of people.

My specifics are:
Acer B115-M, Processor: N2830. Intel graphics
I'll be happy to provide more specific info/outputs if you tell me exactly what you need.
(I'm not an absolute beginer but i'm not a tech geek either so please go gently on me!)

Any ideas on how I should proceed with this? i really need to get the brightness controls working!

Thanks
Kate

Last edited by starflower (2014-12-13 22:48:41)

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#2 2014-12-12 20:48:15

ToZ
Administrator
From: Canada
Registered: 2011-06-02
Posts: 10,948

Re: [Solved] Having problems gettting Brightness Control to work on Mint 17 Xfce

Xfce will use a valid backlight interface, if one exists. From your description, it sounds like you have more than one valid interface and your Xorg sub-system is getting confused.

Lets see if we can get isolate the proper backlight interface. Can you post back the results of the following commands?

  1. Your current kernel boot line:

    cat /proc/cmdline
  2. Info about your video card(s) and drivers:

    lspci -k | grep -A2 VGA
  3. Info about the recognized backlight interfaces:

    for interface in /sys/class/backlight/*; do echo -e "\n $interface"; cat $interface/{brightness,max_brightness,actual_brightness}; done
  4. Your currently loaded kernel modules:

    lsmod
  5. What, if anything, xorg says about backlight:

    cat /var/log/Xorg.0.log | grep -i backlight

Also, does the brightness slider work from the Power Manager Plugin?


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#3 2014-12-13 22:44:57

starflower
Member
From: UK
Registered: 2014-12-12
Posts: 3

Re: [Solved] Having problems gettting Brightness Control to work on Mint 17 Xfce

Thanks for the reply.

I spent several hours searching yesterday and came across this link in Ubuntu forums which I tried and it solved the problem!
http://ubuntuforums.org/showthread.php?t=2235376

It seems you also played a part there as well!

So it seems that the fix is to add the line "video.use_native_backlight=1" in the grub file!

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#4 2014-12-13 22:50:59

ToZ
Administrator
From: Canada
Registered: 2011-06-02
Posts: 10,948

Re: [Solved] Having problems gettting Brightness Control to work on Mint 17 Xfce

starflower wrote:

So it seems that the fix is to add the line "video.use_native_backlight=1" in the grub file!

Yes. The "acpi_backlight=vendor" kernel parameter was replaced in kernel versions 3.13 and greater. Glad you got it figured out.


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