kern/53944: I cannot adjust screen brightness using sysctl -w on Acer Swift 1

[vsatayamas%gmail.com@localhost]

>Number:         53944
>Category:       kern
>Synopsis:       I cannot adjust screen brightness using sysctl -w on Acer Swift 1
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Feb 04 12:45:00 +0000 2019
>Originator:     Vee Satayamas
>Release:        8
>Organization:
Kasetsart University
>Environment:
NetBSD 8.0 BetBSD 8.0 (GENREIC) #0: Tue Jul 17 14:59:51 UTC 2018 mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64
>Description:
I cannot adjust screen brightness using sysctl -w

I tried to adjust my laptop computer, which is Acer Swift 1, LCD screen brightness by these commands:

sysctl -w hw.acpi.acpiout15.brightness=0

sysctl -w hw.acpi.acpiout15.brightness=10

sysctl -w hw.acpi.acpiout15.brightness=50

sysctl -w hw.acpi.acpiout15.brightness=100

sysctl -w hw.acpi.acpiout15.brightness=200

sysctl -w hw.acpi.acpiout15.brightness=1000

But none of those commands change the screen brightness. I got hw.acpi.acpiout15.brightness from ``sysctl -a | grep bright''


>How-To-Repeat:
1. Boot the computer with NetBSD 8
2. Login as root
3. Type the command sysctl -w hw.acpi.acpiout15.brightness=0
4. Press enter
>Fix: