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 -- You received this bug notification because you are a member of Ubuntu 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 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/acpi/+bug/1041846/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs