Making screen brightness keys work on an Acer laptop

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ashishd
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Posts: 2
Joined: Sun May 11, 2014 9:24 pm

Making screen brightness keys work on an Acer laptop

Postby ashishd » Sun May 11, 2014 11:53 pm

Hello everyone,

This is my first post here. I just installed Linux Mint 16 Cinnamon on my Acer Aspire V5 laptop. Everything worked great, except the function key combination for setting the screen brightness wasn't working. The brightness slider would change, but it didn't actually change the brightness. I will share the solution that worked for me and hope it will be helpful to someone.

I noticed that I could change the brightness by modifying /sys/class/backlight/intel_backlight/brightness. Writing a value in that file changed the brightness of my screen. The maximum brightness you can set is in /sys/class/backlight/intel_backlight/max_brightness. You can view it by typing:

Code: Select all

cat /sys/class/backlight/intel_backlight/max_brightness


On my laptop, the maximum brightness is 976. So, to set my brightness to 50%, I could write this:

Code: Select all

echo 488 > /sys/class/backlight/intel_backlight/max_brightness/brightness


There is another directory named acpi_video0 inside /sys/class/backlight. This direcory also has a file named "brightness", but changing it does not affect the brightness. My guess is that for some reason Mint is using acpi_video0 instead of intel_backlight for changing the brightness, and that's why it doesn't work.

Anyway, so one way to fix the problem could be to write a shell script that modifies the brightness file in intel_backlight folder, and associate it with some keyboard shortcut. However, I didn't do that. I tried other solutions that involved editing the /etc/default/grub file as described in many other articles. I tried many combinations, but none of them worked for me.

I fixed the issue by creating a xorg.conf file inside /etc/X11/. I noticed that Mint 16 doesn't have this file by default. I created this file with this command:

Code: Select all

sudo Xorg :1 -configure


This creates a file called xorg.conf.new. Edit this file and add Option "Backlight" "intel_backlight" in Section "Device". Save the file and move this file to /sys/class/backlight:

Code: Select all

mv xorg.conf.new /etc/X11/xorg.conf


Restart your computer, and the brightness keys should work.

JeremyB
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Posts: 6304
Joined: Fri Feb 21, 2014 8:17 am

Re: Making screen brightness keys work on an Acer laptop

Postby JeremyB » Mon May 12, 2014 7:29 am

ashishd wrote:Hello everyone,

This is my first post here. I just installed Linux Mint 16 Cinnamon on my Acer Aspire V5 laptop. Everything worked great, except the function key combination for setting the screen brightness wasn't working. The brightness slider would change, but it didn't actually change the brightness. I will share the solution that worked for me and hope it will be helpful to someone.

I noticed that I could change the brightness by modifying /sys/class/backlight/intel_backlight/brightness. Writing a value in that file changed the brightness of my screen. The maximum brightness you can set is in /sys/class/backlight/intel_backlight/max_brightness. You can view it by typing:

Code: Select all

cat /sys/class/backlight/intel_backlight/max_brightness


On my laptop, the maximum brightness is 976. So, to set my brightness to 50%, I could write this:

Code: Select all

echo 488 > /sys/class/backlight/intel_backlight/max_brightness/brightness


There is another directory named acpi_video0 inside /sys/class/backlight. This direcory also has a file named "brightness", but changing it does not affect the brightness. My guess is that for some reason Mint is using acpi_video0 instead of intel_backlight for changing the brightness, and that's why it doesn't work.

Anyway, so one way to fix the problem could be to write a shell script that modifies the brightness file in intel_backlight folder, and associate it with some keyboard shortcut. However, I didn't do that. I tried other solutions that involved editing the /etc/default/grub file as described in many other articles. I tried many combinations, but none of them worked for me.

I fixed the issue by creating a xorg.conf file inside /etc/X11/. I noticed that Mint 16 doesn't have this file by default. I created this file with this command:

Code: Select all

sudo Xorg :1 -configure


This creates a file called xorg.conf.new. Edit this file and add Option "Backlight" "intel_backlight" in Section "Device". Save the file and move this file to /sys/class/backlight:

Code: Select all

mv xorg.conf.new /etc/X11/xorg.conf


Restart your computer, and the brightness keys should work.


I just created a file called 20-intel.conf and placed it in /usr/share/X11/xorg.conf.d

This file contains

Code: Select all

Section "Device"
        Identifier  "card0"
        Driver      "intel"
        Option      "Backlight"  "intel_backlight"
        BusID       "PCI:0:2:0"

EndSection


The only difference I saw was in the Xorg.0.log but my backlight worked. Before adding the file the log would say acpi_video0 as backlight.
Now

Code: Select all

cat /var/log/Xorg.0.log | grep backlight
shows

Code: Select all

[    27.089] (**) intel(0): Option "Backlight" "intel_backlight"
[    27.090] (**) intel(0): found backlight control interface intel_backlight (type 'user')


Did you ever try the grub boot option

Code: Select all

acpi_backlight=vendor
?

User avatar
hal8000
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Posts: 281
Joined: Sun May 04, 2008 2:04 pm
Location: UK

Re: Making screen brightness keys work on an Acer laptop

Postby hal8000 » Mon May 12, 2014 5:06 pm

The following worked for me on Acer 5734Z with Mint 16 KDE. You can find out the chipset in Mint using:

sudo inxi -Gx

You can also find the PCI bus ID with:

lspci | grep -i vga

If you have hotkeys for brightness like Fn + brightness you can check these have been recognised
by typing:
xev

This will produce a keycode if the keys have been detected, if all checks out and you have an Intel chipset
then just creating /usr/share/X11/xorg.conf.d/20-intel.conf with following contents:

Section "Device"
Identifier "card0"
Driver "intel"
Option "Backlight" "intel_backlight"
BusID "PCI:0:2:0"
EndSection

More details on this page:

http://itsfoss.com/fix-brightness-ubuntu-1310/

ashishd
Level 1
Level 1
Posts: 2
Joined: Sun May 11, 2014 9:24 pm

Re: Making screen brightness keys work on an Acer laptop

Postby ashishd » Mon May 12, 2014 6:46 pm

JeremyB wrote:Did you ever try the grub boot option

Code: Select all

acpi_backlight=vendor
?


Yes, I tried that, and it did not work. It works on another laptop of mine though (that has Ubuntu 12.04, and had the same issue). However, it does not work on my Acer laptop (with Mint 16). Creating a xorg.conf file is the only solution that seems to work.

wewa
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Posts: 32
Joined: Tue Jan 24, 2012 4:20 am

Re: Making screen brightness keys work on an Acer laptop

Postby wewa » Wed Nov 12, 2014 10:49 am

I have a Gateway (made by Acer) NV55 notebook. Intel chipset.

Code: Select all

sudo Xorg :1 -configure


gives me a error:

Number of created screens does not match number of detected devices.
Configuration failed.
(EE) Server terminated with error (2). Closing log file.


Code: Select all

X.Org X Server 1.15.1
Release Date: 2014-04-13
X Protocol Version 11, Revision 0
Build Operating System: Linux 3.2.0-37-generic x86_64 Ubuntu
Current Operating System: Linux NV55C 3.13.0-24-generic #46-Ubuntu SMP Thu Apr 10 19:11:08 UTC 2014 x86_64
Kernel command line: BOOT_IMAGE=/boot/vmlinuz-3.13.0-24-generic root=UUID=9cd8fbe3-1136-4e47-8334-3ef2a53c4f7a ro quiet splash acpi_backlight=vendor vt.handoff=7
Build Date: 16 April 2014  01:36:29PM
xorg-server 2:1.15.1-0ubuntu2 (For technical support please see http://www.ubuntu.com/support)
Current version of pixman: 0.30.2
   Before reporting problems, check http://wiki.x.org
   to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting,
   (++) from command line, (!!) notice, (II) informational,
   (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/var/log/Xorg.1.log", Time: Wed Nov 12 04:46:35 2014
setversion 1.4 failed: Permission denied
List of video drivers:
   sisusb
   openchrome
   neomagic
   modesetting
   vboxvideo
   tdfx
   siliconmotion
   intel
   mga
   nouveau
   savage
   ati
   trident
   vmware
   qxl
   cirrus
   spiceqxl
   sis
   s3
   radeon
   mach64
   r128
   vesa
   fbdev
(++) Using config file: "/home/gateway/xorg.conf.new"
(==) Using system config directory "/usr/share/X11/xorg.conf.d"
Number of created screens does not match number of detected devices.
  Configuration failed.
(EE) Server terminated with error (2). Closing log file.


any suggestions?

Thanks.


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