Brightness settings changes have no effect.

[Nico T]

On my laptop (acer aspire one V5-131) which uses Ubuntu 13.04, the change of the brightness settings have no effect on the brightness in the settings application.

When I press the shortcut for changing the brightness (Fn+Left & Fn+Right), the notification of the new brightness level is correctly displayed but again it has no effect on the brightness of the screen (and it neither update the level in the settings application).

Please, see in the attached file (Brightness.txt) what I do for changing the brightness on my computer from the console.

I don't know anything about the settings software stack but since it works from the console I don't think it is a driver problem but rather a software problem somewhere or maybe a missing symlink. Though the keyboard shortcut are not working properly, the problem could also be below gnome-control-center.

Please contact me for any question or if I can be of any help for the correction.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: gnome-control-center 1:3.6.3-0ubuntu24.1
ProcVersionSignature: Ubuntu 3.8.0-33.48-generic 3.8.13.11
Uname: Linux 3.8.0-33-generic i686
ApportVersion: 2.9.2-0ubuntu8.5
Architecture: i386
Date: Sun Nov 24 07:39:09 2013
EcryptfsInUse: Yes
ExecutablePath: /usr/bin/gnome-control-center
InstallationDate: Installed on 2013-06-10 (166 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release i386 (20130424)
MarkForUpload: True
SourcePackage: gnome-control-center
UpgradeStatus: No upgrade log present (probably fresh install)
usr_lib_gnome-control-center:
 deja-dup 26.0-0ubuntu1
 gnome-control-center-signon 0.1.6bzr13.04.05-0ubuntu1.1
 gnome-control-center-unity 1.3daily13.06.19~13.04-0ubuntu1
 indicator-datetime 12.10.3daily13.03.26-0ubuntu1

[N1ck 7h0m4d4k15 (nicktux)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. This is a known problem with some ACPI backlight drivers.

Please read this article in order to debugging more this issue
https://wiki.ubuntu.com/Kernel/Debugging/Backlight

Please provide the additional information that are needed according to above article.

Best Regards
    NikTh

[Nico T (nlko)]

Here are the requested informations.

As you will see there are two folders in /sys/class/backlight

When I use the keyboards shortcuts to modify the brightness, the file /sys/class/backlight/acpi_video0/brightness is modified but it has no effect on the actual brightness.

When I manually write the brightness into the file /sys/class/backlight/intel_backlight/brightness, the actual brightness is modified.

Some software (like cairo dock manage to change the brightness). I guess they use the right folder.

Nicolas

[Nico T (nlko)]

More information

acpi_backlight=vendor
    Shortcut doesn't work at all (Fn+Left and Fn+Right). there is no OSD displayed anymore
    I can change the backlight from the system settings (doing so modifies the /sys/class/backlight/intel_backlight/brightness file)
    Writting from the console myself in /sys/class/backlight/intel_backlight/brightness changes the backlight level (8 dimm : the screen is almost off).

video.use_bios_initial_backlight=0 : NO CHANGE compare to the initial report. I can control the backlight level from the console with the file /sys/class/backlight/intel_backlight/brightness file (8 dimm : the screen is almost off) but the software modifies the brigtness in the acpi folder instead.

atkbd.softraw=0 :
   NO CHANGE compare to the initial report. I can control the backlight level from the console with the file /sys/class/backlight/intel_backlight/brightness file (8 dimm : the screen is almost off) but the software modifies the brigtness in the acpi folder instead.
   Show key result is
   Left 0xe0 0x4b 0xe0 0xcb
   Right 0xe0 0x4d 0xe0 0xcd

[Jakob Mühldorfer (jmuehldorfer)]

I can control the backlight via FN-keys, however there is no OSD notification.
I use Ubuntu 13.10, kernel 3.11.0-14 and as grub commandline "quiet nosplash acpi_osi= acpi_backlight=vendor"

[Nico T (nlko)]

I confirm what Jankob said. With the same parameters on the grub command line, I have the same behavior on my 13.4 (kernel 3.8.0-34) : it works but no OSD notification.

[Launchpad Janitor (janitor)]

[Expired for Ubuntu because there has been no activity for 60 days.]