https://bugs.kde.org/show_bug.cgi?id=455347
Bug ID: 455347
Summary: Cannot reliably adjust screen brightness after 5.25
update
Product: Powerdevil
Version: 5.25.0
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: plasma-b...@kde.org
Reporter: jramirez...@gmail.com
Target Milestone: ---
SUMMARY
After updating to KDE Plasma 5.25 the screen brightness control is showing some
very erratic behavior. As I am increasing brightness it goes up and down and
then up again until I reach 100% with as much as 20% effective brightness.
My `/sys/class/backlight/intel_backlight/max_brightness` shows `120000`. But
monitoring `/sys/class/backlight/intel_backlight/brightness` shows it doesn't
go upper than 17000.
Interestingly, as I go on and on trying to increase brightness, the value in
`/sys/class/backlight/intel_backlight/brightness` increases and decreases with
not apparent pattern.
I checked the journal to see if there were any errors and found this:
```
Jun 15 10:01:13 hypernova kernel: ACPI BIOS Error (bug): Could not resolve
symbol [\_SB.PCI0.PEG0.PEGP.BRT6.LCD], AE_NOT_FOUND (20210331/psargs-330)
Jun 15 10:01:13 hypernova kernel:
Jun 15 10:01:13 hypernova kernel: No Local Variables are initialized for Method
[BRT6]
Jun 15 10:01:13 hypernova kernel:
Jun 15 10:01:13 hypernova kernel: Initialized Arguments for Method [BRT6]: (2
arguments defined for method invocation)
Jun 15 10:01:13 hypernova kernel: Arg0: 000000000a60e3c0 <Obj>
Integer 0000000000000001
Jun 15 10:01:13 hypernova kernel: Arg1: 000000001176d691 <Obj>
Integer 0000000000000000
Jun 15 10:01:13 hypernova kernel:
Jun 15 10:01:13 hypernova kernel: ACPI Error: Aborting method
\_SB.PCI0.PEG0.PEGP.BRT6 due to previous error (AE_NOT_FOUND)
(20210331/psparse-529)
Jun 15 10:01:13 hypernova kernel: ACPI Error: Aborting method \EV5 due to
previous error (AE_NOT_FOUND) (20210331/psparse-529)
Jun 15 10:01:13 hypernova kernel: ACPI Error: Aborting method \SMEE due to
previous error (AE_NOT_FOUND) (20210331/psparse-529)
Jun 15 10:01:13 hypernova kernel: ACPI Error: Aborting method \SMIE due to
previous error (AE_NOT_FOUND) (20210331/psparse-529)
Jun 15 10:01:13 hypernova kernel: ACPI Error: Aborting method \NEVT due to
previous error (AE_NOT_FOUND) (20210331/psparse-529)
Jun 15 10:01:13 hypernova kernel: ACPI Error: Aborting method
\_SB.PCI0.LPCB.ECDV._Q66 due to previous error (AE_NOT_FOUND)
(20210331/psparse-529)
```
Which indicates some hardware-related issue, which is weird because I haven
updated my laptop's firmware recently. Besides, echoing to
`/sys/class/backlight/intel_backlight/brightness` works as expected.
Also, a think I am not alone in this one, see this reddit thread:
https://www.reddit.com/r/kdeneon/comments/vcpx9c/cant_adjust_brightness/
STEPS TO REPRODUCE
1. Try to increase/decrease screen brightness
OBSERVED RESULT
Screen brightness shows erratic behavior.
EXPECTED RESULT
Screen brightness should increase or decrease accordingly.
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 5.25.0
(available in About System)
KDE Plasma Version: 5.25.0
KDE Frameworks Version: 5.95.0
Qt Version: 5.15.4
ADDITIONAL INFORMATION
Laptop model: Dell XPS 15 (7590).
Graphics platform: X11
Graphics processor: Mesa Intel UHD Graphics 630
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