KDE backlight control - backlighthelper not running?

[Lukáš Tinkl]

Dne Ne 4. března 2012 13:58:36, Maciek Borzecki napsal(a):
> I'm seeing an odd issue with KDE and screen backlight control. I'm
> running Thinkpad T60, with KDE 4.7 (from updates) and unfortunately
> the backlight control does not work. Pressing Fn+Home/Fn+End does not
> seem to have any effect. I normally have to tweak hotkey mask to
> something like 0xffffff in order to have the proper key events appear,
> and it does work but only in Gnome and Xfce.
> Before anyone suggests reinstalling bash, I've already done it
> (otherwise it wouldn't work in Xfce).
> 
> Looking at the logs:
> - kded debugs:
> kded(2495) PowerDevil::BackendLoader::loadBackend: Loading UPower backend...
> kded(2495) PowerDevil::BackendLoader::loadBackend: Success!
> kded(2495) KDEDPowerDevil::init: Backend loaded, loading core
> kded(2495) PowerDevil::Core::loadCore: Core loaded, initializing backend
> kded(2495) PowerDevilUPowerBackend::brightness: Screen brightness:  0
> <---- why is current brightness 0?
> kded(2495) PowerDevilUPowerBackend::init: current screen brightness:  0
> kded(2495) PowerDevilUPowerBackend::init: Can suspend
> kded(2495) PowerDevilUPowerBackend::init: Can hibernate
> kded(2495) PowerDevil::Core::onBackendReady: Backend is ready, KDE
> Power Management system initialized
> 
> - messages - nothing about backlight helper being activated
> - .xsession-errors - nothing related
> 
> Since it does not work with 4.7 from updates, I updated to 4.8 from
> kde48 repo. Unfortunately, with similar results.
> 
> As a last resort I checked with KDE live spin, and amazingly,
> backlight control works. So something between the current version of
> packages and the one from live KDE spin, things got broken.
> 
> Correct me if I'm wrong, but looking at the code, I see that in order
> to control the backlight, there's a helper program
> (/usr/libexec/kde4/backlighthelper) which starts through dbus
> activation, and exposes brigthness, setbrigthness methods. I take that
> once started the demon should remain running at lest for some time.
> Now in KDE spin, that happens to be the case, I can clearly see
> backlighthelper process listed in ps output (there are also logs in
> messages, that activation of backlighthelper was successful).
> However, right now, no such log is to be found, as if for some reason
> backlight helper does not get started.
> 
> Any ideas on how to proceed with debugging this?
> 
> Thanks,
> --
> Maciek Borzecki
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Please post the result from "ls /sys/class/backlight/" on both systems
-- 
Lukáš Tinkl <ltinkl at redhat.com>
Software Engineer - Base Operating Systems Brno
KDE developer <lukas at kde.org>
Red Hat Inc.                               http://cz.redhat.com