Bug 403125

Summary: Setting minimal brightness level on many latest Intel-based devices turn off backlight
Product: [Unmaintained] Powerdevil Reporter: RussianNeuroMancer <russianneuromancer>
Component: generalAssignee: Plasma Bugs List <plasma-bugs>
Status: RESOLVED DUPLICATE    
Severity: major CC: aubergine, bugseforuns, eliadevito, hejsekvojtech, hoffmann_lorenz, lucia.mrenica, nate, pascal
Priority: NOR    
Version First Reported In: 5.15.5   
Target Milestone: ---   
Platform: unspecified   
OS: Linux   
Latest Commit: Version Fixed In:
Sentry Crash Report:

Description RussianNeuroMancer 2019-01-12 03:27:07 UTC 
SUMMARY
Some HP devices (probably many) such as HP EliteBook Folio G1 and HP Elite x2 1013 G3 turn off backlight if user set minimal brightness level. Due to unresolved issues with hp_wmi brightness hotkeys doesn't work, so user left with black screen and no convenient option that would let him turn backlight on again. (Hence major severity.)

Same happen not only on HP devices but also on other devices, such as GPD Win 2 and ASUS UX550GE.

I propose to limit minimal brightness level for such devices to prevent backlight from turning off.

STEPS TO REPRODUCE
1. Set brightness to minimal level

OBSERVED RESULT
Brightness is turned off

EXPECTED RESULT
Brightness is set to minimal level, but not turned off.

SOFTWARE/OS VERSIONS
Linux: Kubuntu 18.10
KDE Plasma Version: Plasma 5.13.5
KDE Frameworks Version: 5.50
Qt Version: 5.11.1

ADDITIONAL INFORMATION
Intel not planning to resolve this issue in driver: https://bugs.freedesktop.org/show_bug.cgi?id=108618
Similar issue is resolved in Gnome Settings Daemon:
https://gitlab.gnome.org/GNOME/gnome-settings-daemon/issues/54
https://gitlab.gnome.org/GNOME/gnome-settings-daemon/merge_requests/17
Comment 1 Nate Graham 2020-07-22 13:52:04 UTC 
Can confirm with every Intel-based laptop I've ever owned. Thanks for providing the information indicating that we'll need to handle this ourselves. Still... meh. :( Sad that they don't want to handle it properly themselves.
Comment 2 Nate Graham 2020-07-22 14:01:43 UTC 
*** Bug 362830 has been marked as a duplicate of this bug. ***
Comment 3 Lorenz Hoffmann 2021-05-29 13:22:20 UTC 
Can confirm this from a Lenovo Yoga. A workaround would be to set two keyboard shortcuts to change brightness levels up and down.
Comment 4 Vojtěch 2022-04-23 18:30:51 UTC 
Can confirm this happening on Lenovo ThinkPad E580 (i5 8250U + UHD 620).
Comment 5 Aidan Coombs 2023-08-19 05:15:10 UTC 
Similar issue on my Lenovo ThinkBook (Intel 11th gen/Arch Linux/ZEN kernel).
When I use the brightness adjustment keys (which fortunately do work) to set the screen brightness to 0%, the backlight turns off completely (`cat /sys/class/backlight/intel_backlight/brightness` gives 0). 
However, when I use the Battery & Brightness plasmoid to set it to 0%, the backlight goes to minimum brightness but does not turn off (running the earlier command gives 1).
This inconsistency is unusual but should surely mean that the backlight issues are easier to fix.
I notice that on some devices, /sys/class/backlight/intel_backlight/max_brightness is a very high number, like 122000; on my device, it's 15360, so minimum brightness isn't too bad--especially in bed, late at night.
Comment 6 Nate Graham 2023-08-21 17:50:17 UTC 
Fixed for Plasma 6.

*** This bug has been marked as a duplicate of bug 430439 ***