It seems that power management is broken. Whenever I resume my laptop keyboard backlight is off eventhough it was ON before. All 3 modes (AC/bat/lowbat) has not been changed for at least a month and it has no value set in all 3 modes for keyboard backlight. I am having other issue with recent Plasma - https://bugs.kde.org/show_bug.cgi?id=391558, probably related? ---------------------------- This is part of journal after resuming: bře 13 14:50:17 NEHEZ-DELL org_kde_powerdevil[1067]: [14::50:17.102] unknown: Kbd backlight brightness value: 0 bře 13 14:50:17 NEHEZ-DELL org_kde_powerdevil[1067]: [14::50:17.102] unknown: set kbd backlight value: 0 bře 13 14:50:17 NEHEZ-DELL org_kde_powerdevil[1067]: [14::50:17.114] unknown: Keyboard brightness changed!!
Kernel: 4.15.7-1-MANJARO x86_64
Does rolling back to an earlier kernel help?
I ask because Manjaro is a rolling distro that gets kernel updates pretty frequently, and you indicated that yo didn't change any powerdevil settings. In the discussion linked to from Bug 391558, you also indicated that there were no updates to powerdevil, but there was a kernel update. Therefore, it seems very likely that this was caused by a kernel regression. If indeed it's a kernel regression, the issue should be reported on https://bugzilla.kernel.org/. If the problem persists after you roll back the kernel to an earlier version, then please re-open the bug.
I went back to kernel 4.14, even 6 steps back, nothing has changed. Then I upgraded to the latest 4.14 again and voila - backlight works as expected. That's a magic - I don't like these bugs ;)