A few weeks ago, I enabled i2c-dev and nct6775 kernel modules, because I I’m using OpenRGB to control some RGB LED-strips connected to my mainboard. This is working fine so far.
A side effect of that was, that my (desktop) system was now able to control the screen brightness of my display. These options appeared in the system settings tab for “Energy Saving”. But since everything worked fine, I didn’t thought about it anymore.
Now, maybe until a recent update, I’m not totally sure, I get this:
I noticed it, when the screen stopped turning off after the set time.
$ journalctl --user -p4
Apr 30 13:29:14 org_kde_powerdevil[26664]: org.kde.powerdevil: [DDCutilBrightness::setBrightness] failed, trying to detect()
Apr 30 13:29:15 systemd-coredump[26717]: Process 26664 (org_kde_powerde) of user 1000 dumped core.
Stack trace of thread 26664:
#0 0x00007f73e8ed9ef5 raise (libc.so.6 + 0x3cef5)
#1 0x00007f73e8ed9f80 __restore_rt (libc.so.6 + 0x3cf80)
#2 0x00007f73e8ed9ef5 raise (libc.so.6 + 0x3cef5)
#3 0x00007f73e8ec3862 abort (libc.so.6 + 0x26862)
#4 0x00007f73e8ec3747 __assert_fail_base.cold (libc.so.6 + 0x26747)
#5 0x00007f73e8ed2646 __assert_fail (libc.so.6 + 0x35646)
#6 0x00007f73e16f6c57 n/a (libddcutil.so.4 + 0x1bc57)
#7 0x00007f73e16eb530 ddca_open_display2 (libddcutil.so.4 + 0x10530)
#8 0x00007f73e17c6855 n/a (powerdevilupowerbackend.so + 0x17855)
#9 0x00007f73e17c7622 n/a (powerdevilupowerbackend.so + 0x18622)
#10 0x00007f73e95349e6 n/a (libQt5Core.so.5 + 0x2ed9e6)
#11 0x00007f73e9538a7b _ZN6QTimer7timeoutENS_14QPrivateSignalE (libQt5Core.so.5 + 0x2f1a7b)
#12 0x00007f73e952a0cf _ZN7QObject5eventEP6QEvent (libQt5Core.so.5 + 0x2e30cf)
#13 0x00007f73e94fd68a _ZN16QCoreApplication15notifyInternal2EP7QObjectP6QEvent (libQt5Core.so.5 + 0x2b668a)
#14 0x00007f73e9555515 _ZN14QTimerInfoList14activateTimersEv (libQt5Core.so.5 + 0x30e515)
#15 0x00007f73e9555dfa n/a (libQt5Core.so.5 + 0x30edfa)
#16 0x00007f73e751202c g_main_context_dispatch (libglib-2.0.so.0 + 0x5402c)
#17 0x00007f73e7565b59 n/a (libglib-2.0.so.0 + 0xa7b59)
#18 0x00007f73e750f781 g_main_context_iteration (libglib-2.0.so.0 + 0x51781)
#19 0x00007f73e9556191 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt5Core.so.5 + 0x30f191)
#20 0x00007f73e94fbfec _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt5Core.so.5 + 0x2b4fec)
#21 0x00007f73e95044a4 _ZN16QCoreApplication4execEv (libQt5Core.so.5 + 0x2bd4a4)
#22 0x0000557eb76281eb n/a (org_kde_powerdevil + 0x61eb)
#23 0x00007f73e8ec4b25 __libc_start_main (libc.so.6 + 0x27b25)
#24 0x0000557eb762825e _start (org_kde_powerdevil + 0x625e)
Stack trace of thread 26674:
#0 0x00007f73e8f9d60d recvmsg (libc.so.6 + 0x10060d)
#1 0x00007f73e745c257 n/a (libudev.so.1 + 0x10257)
#2 0x00007f73e745cc8b udev_monitor_receive_device (libudev.so.1 + 0x10c8b)
#3 0x00007f73e16fa232 n/a (libddcutil.so.4 + 0x1f232)
#4 0x00007f73e75400c1 n/a (libglib-2.0.so.0 + 0x820c1)
#5 0x00007f73e7f82299 start_thread (libpthread.so.0 + 0x9299)
#6 0x00007f73e8f9c053 __clone (libc.so.6 + 0xff053)
Stack trace of thread 26673:
#0 0x00007f73e8f9137f __poll (libc.so.6 + 0xf437f)
#1 0x00007f73e7565ae8 n/a (libglib-2.0.so.0 + 0xa7ae8)
#2 0x00007f73e7511593 g_main_loop_run (libglib-2.0.so.0 + 0x53593)
#3 0x00007f73e2987558 n/a (libgio-2.0.so.0 + 0x102558)
#4 0x00007f73e75400c1 n/a (libglib-2.0.so.0 + 0x820c1)
#5 0x00007f73e7f82299 start_thread (libpthread.so.0 + 0x9299)
#6 0x00007f73e8f9c053 __clone (libc.so.6 + 0xff053)
Stack trace of thread 26670:
#0 0x00007f73e8f9137f __poll (libc.so.6 + 0xf437f)
#1 0x00007f73e87da63b n/a (libxcb.so.1 + 0xc63b)
#2 0x00007f73e87dc37b xcb_wait_for_event (libxcb.so.1 + 0xe37b)
#3 0x00007f73e3c24161 n/a (libQt5XcbQpa.so.5 + 0x5e161)
#4 0x00007f73e931507f n/a (libQt5Core.so.5 + 0xce07f)
#5 0x00007f73e7f82299 start_thread (libpthread.so.0 + 0x9299)
#6 0x00007f73e8f9c053 __clone (libc.so.6 + 0xff053)
Stack trace of thread 26672:
#0 0x00007f73e8f9137f __poll (libc.so.6 + 0xf437f)
#1 0x00007f73e7565ae8 n/a (libglib-2.0.so.0 + 0xa7ae8)
#2 0x00007f73e750f781 g_main_context_iteration (libglib-2.0.so.0 + 0x51781)
#3 0x00007f73e750f7d2 n/a (libglib-2.0.so.0 + 0x517d2)
#4 0x00007f73e75400c1 n/a (libglib-2.0.so.0 + 0x820c1)
#5 0x00007f73e7f82299 start_thread (libpthread.so.0 + 0x9299)
#6 0x00007f73e8f9c053 __clone (libc.so.6 + 0xff053)
Stack trace of thread 26671:
#0 0x00007f73e8f9137f __poll (libc.so.6 + 0xf437f)
#1 0x00007f73e7565ae8 n/a (libglib-2.0.so.0 + 0xa7ae8)
#2 0x00007f73e750f781 g_main_context_iteration (libglib-2.0.so.0 + 0x51781)
#3 0x00007f73e9556191 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt5Core.so.5 + 0x30f191)
#4 0x00007f73e94fbfec _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt5Core.so.5 + 0x2b4fec)
#5 0x00007f73e9313e92 _ZN7QThread4execEv (libQt5Core.so.5 + 0xcce92)
#6 0x00007f73e97b5098 n/a (libQt5DBus.so.5 + 0x17098)
#7 0x00007f73e931507f n/a (libQt5Core.so.5 + 0xce07f)
#8 0x00007f73e7f82299 start_thread (libpthread.so.0 + 0x9299)
#9 0x00007f73e8f9c053 __clone (libc.so.6 + 0xff053)
Stack trace of thread 26685:
#0 0x00007f73e8f93bf3 pselect (libc.so.6 + 0xf6bf3)
#1 0x00007f73e4d65524 n/a (libusbmuxd-2.0.so.6 + 0x2524)
#2 0x00007f73e4d668a9 n/a (libusbmuxd-2.0.so.6 + 0x38a9)
#3 0x00007f73e7f82299 start_thread (libpthread.so.0 + 0x9299)
#4 0x00007f73e8f9c053 __clone (libc.so.6 + 0xff053)
Apr 30 13:29:15 org_kde_powerdevil[26712]: org.kde.powerdevil: Handle button events action could not check for screen configuration
Apr 30 13:29:16 org_kde_powerdevil[26712]: org.kde.powerdevil: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds not supported"
Apr 30 13:29:16 org_kde_powerdevil[26712]: org.kde.powerdevil: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds not supported"
Since I the last thing I changed was the kernel to 5.12, the first thing was to reboot the 5.10 LTS kernel, but that didn’t changed anything.
Then I removed (== not explicitly loaded) the i2c-dev and nct6775 kernel modules and after a reboot, the error was gone (with it the settings for screen brightness), but now I can’t control my LEDs anymore.
So I’m unsure what to try next. Maybe it’s just a configuration issue, maybe something garbled up…
But I’m also unsure what the “Power Management Service” actually is!?
Is it upower.service or plasma-powerdevil.service – or something else? I player around with these and loading/unloading the said kernel modules with modprobe… but basically the power management page goes away as soon as the modules are loaded.
Interestingly this worked perfectly fine for a while (controlling RGB LEDs using OpenRGB and power management at the same time).
Any ideas? 
Happy to provide more detailed information if needed!