Public bug reported:
When I originally installed Ubuntu 12.04 it came with kernel 3.2.0-23
and the screen brightness controls on my Samsung NP530U3C worked out-of-
the-box.
However after I applied the updates and rebooted into the latest kernel
(3.2.0-29) the screen brightness controls no longer work.
Symptoms:
Press screen brightness function keys to either increase or decrease brightness
OR try changing the screen brightness in either KDE or GNOME with the 'slider'
in the respective power management GUI programs
Expected Result and Result with kernel 3.2.0-23:
Screen brightness increases or decreases accordingly
Actual Result with kernel 3.2.0-29:
Screen flickers a bit but the brightness level seems 'stuck' and won't change.
Workaround:
The funny thing is that manipulating the /sys/class/backlight/acpi_video0 files
directly works, so:
echo 47 | sudo tee /sys/class/backlight/acpi_video0/brightness # set brightness
to approx 50% of the maximum
---
ApportVersion: 2.0.1-0ubuntu12
Architecture: amd64
DistroRelease: Ubuntu 12.04
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64
(20120425)
Package: acpi 1.6-1
PackageArchitecture: amd64
ProcEnviron:
LANGUAGE=en_AU:en
TERM=xterm
PATH=(custom, no user)
LANG=en_AU.UTF-8
SHELL=/bin/bash
ProcVersionSignature: Ubuntu 3.2.0-29.46-generic 3.2.24
Tags: precise
Uname: Linux 3.2.0-29-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo
** Affects: acpi (Ubuntu)
Importance: Undecided
Status: New
** Tags: apport-collected precise
** Tags added: apport-collected precise
** Description changed:
When I originally installed Ubuntu 12.04 it came with kernel 3.2.0-23
and the screen brightness controls on my Samsung NP530U3C worked out-of-
the-box.
However after I applied the updates and rebooted into the latest kernel
(3.2.0-29) the screen brightness controls no longer work.
Symptoms:
Press screen brightness function keys to either increase or decrease
brightness OR try changing the screen brightness in either KDE or GNOME with
the 'slider' in the respective power management GUI programs
Expected Result and Result with kernel 3.2.0-23:
Screen brightness increases or decreases accordingly
Actual Result with kernel 3.2.0-29:
Screen flickers a bit but the brightness level seems 'stuck' and won't change.
Workaround:
The funny thing is that manipulating the /sys/class/backlight/acpi_video0
files directly works, so:
echo 47 | sudo tee /sys/class/backlight/acpi_video0/brightness # set
brightness to approx 50% of the maximum
+ ---
+ ApportVersion: 2.0.1-0ubuntu12
+ Architecture: amd64
+ DistroRelease: Ubuntu 12.04
+ InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64
(20120425)
+ Package: acpi 1.6-1
+ PackageArchitecture: amd64
+ ProcEnviron:
+ LANGUAGE=en_AU:en
+ TERM=xterm
+ PATH=(custom, no user)
+ LANG=en_AU.UTF-8
+ SHELL=/bin/bash
+ ProcVersionSignature: Ubuntu 3.2.0-29.46-generic 3.2.24
+ Tags: precise
+ Uname: Linux 3.2.0-29-generic x86_64
+ UpgradeStatus: No upgrade log present (probably fresh install)
+ UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo
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Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/1041846
Title:
Regression - screen brightness worked with kernel 3.2.0-23 but not
with 3.2.0-29
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https://bugs.launchpad.net/ubuntu/+source/acpi/+bug/1041846/+subscriptions
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