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

starflower · 2014-12-12 15:13:01

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)

ToZ · 2014-12-12 20:48:15

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?

Your current kernel boot line:
```
cat /proc/cmdline
```
Info about your video card(s) and drivers:
```
lspci -k | grep -A2 VGA
```

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

Your currently loaded kernel modules:
```
lsmod
```
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?

starflower · 2014-12-13 22:44:57

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!

ToZ · 2014-12-13 22:50:59

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.

Xfce Forum

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

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

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

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

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

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

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

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

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