Similar to https://bugs.kde.org/show_bug.cgi?id=368221 but on a Dell Inspiron 13 $ lsb_release -a Distributor ID:neon Description:KDE neon User Edition 5.12 Release: 16.04 Codename: xenial $ uname -a Linux faster 4.13.0-36-generic #40~16.04.1-Ubuntu SMP Fri Feb 16 23:25:58 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux After 5.12 update the brightness of the screen cannot be adjusted from the keyboard, from the "Brightness and Battery" widget and even from "Energy Saving" in System Settings. From the keyboard: pressing Fn and brightness up/down keys (F12, F11 respectively) does not change the brightness of the screen. The screen brightness indicator is shown and there are changes in the bar reflective of the key combination pressed but no change in screen brightness. I ran the command `journalctl -af` and this was the only output when changing the brightness from the keyboard: Mar 09 15:53:53 faster dbus[1129]: [system] Activating service name='org.kde.powerdevil.backlighthelper' (using servicehelper) Mar 09 15:53:53 faster org.kde.powerdevil.backlighthelper[6958]: QDBusArgument: read from a write-only object Mar 09 15:53:53 faster org.kde.powerdevil.backlighthelper[6958]: QDBusArgument: read from a write-only object Mar 09 15:53:53 faster org.kde.powerdevil.backlighthelper[6958]: QDBusArgument: read from a write-only object Mar 09 15:53:53 faster dbus[1129]: [system] Successfully activated service 'org.kde.powerdevil.backlighthelper' From the Brightness and Battery widget and Energy Saving in System Settings: dragging control has no impact on the brightness of the screen. I ran the command `journalctl -af` and this was the only output when changing the brightness from the settings mentioned above: Mar 09 15:56:04 faster dbus[1129]: [system] Activating service name='org.kde.powerdevil.backlighthelper' (using servicehelper) Mar 09 15:56:04 faster org.kde.powerdevil.backlighthelper[7014]: QDBusArgument: read from a write-only object Mar 09 15:56:04 faster org.kde.powerdevil.backlighthelper[7014]: QDBusArgument: read from a write-only object Mar 09 15:56:04 faster org.kde.powerdevil.backlighthelper[7014]: QDBusArgument: read from a write-only object Mar 09 15:56:04 faster dbus[1129]: [system] Successfully activated service 'org.kde.powerdevil.backlighthelper'
Updated to reflect issue still present after upgrade to 5.12.3 and packages libpowerdevilcore2/xenial,now 4:5.12.3-0neon+16.04+xenial+build63 amd64 [installed,automatic] libpowerdevilui5/xenial,now 4:5.12.3-0neon+16.04+xenial+build63 amd64 [installed,automatic] libupower-glib3/xenial-updates,now 0.99.4-2ubuntu0.3 amd64 [installed,automatic] powerdevil/xenial,now 4:5.12.3-0neon+16.04+xenial+build63 amd64 [installed,automatic] powerdevil-data/xenial,xenial,xenial,now 4:5.12.3-0neon+16.04+xenial+build63 all [installed,automatic] powermgmt-base/xenial,xenial,now 1.31+nmu1 all [installed]
What kind of information is required to proceed with troubleshooting this issue?
I discovered that clicking the Apply button is required when changing the screen brightness setting from the "Energy saving" menu of the system settings panel. That is not intuitive, one would expect the luminosity of the screen to change along with the sliding of the control. For a ZBook (Xeon) HP laptop workstation, the settings cannot be modified using the fn/f5 fn/f6 keyboard combinations.
Adding "acpi_backlight=native" to GRUB_CMDLINE_LINUX in /etc/default/grub solved the issue.
So it would be up to your distro to supply that, then. Thanks for checking in!