Cannot turn off keyboard backlight permanently

earthw0rmjim · 10-03-2020, 12:43 PM

Hi,

I have a Chuwi GemiBook laptop (with Intel Celeron J4115 CPU) and i'd like to turn off its keyboard backlight permanently.
It can be turned off with one of the Fn keys, but the turned off state is not persisted through reboots.
EDIT: I'm running Debian stable with i3wm.

Found the following ArchWiki article:
https://wiki.archlinux.org/index.php/keyboard_backlight
But i don't seem to have any keyboard related devices under /sys/class/leds.

Code:

$ brightnessctl --list
Available devices:
Device 'intel_backlight' of class 'backlight':
        Current brightness: 3200 (33%)
        Max brightness: 9600

Device 'phy0-led' of class 'leds':
        Current brightness: 1 (100%)
        Max brightness: 1

Device 'mmc2::' of class 'leds':
        Current brightness: 0 (0%)
        Max brightness: 255

Device 'input0::scrolllock' of class 'leds':
        Current brightness: 0 (0%)
        Max brightness: 1

Device 'input0::capslock' of class 'leds':
        Current brightness: 0 (0%)
        Max brightness: 1

Device 'mmc1::' of class 'leds':
        Current brightness: 0 (0%)
        Max brightness: 255

Device 'input0::numlock' of class 'leds':
        Current brightness: 0 (0%)
        Max brightness: 1

Device 'mmc0::' of class 'leds':
        Current brightness: 0 (0%)
        Max brightness: 255

intel_backlight is the display brightness and setting phy0-led to 0 does not seem to have any effect.

Checked the BIOS as well, didn't find any settings related to the keyboard backlight.

I'd really appreciate any advice.
Thanks in advance!

sgosnell · 10-03-2020, 01:03 PM

What distro, what desktop environment?

earthw0rmjim · 10-03-2020, 01:16 PM

Right, forgot to mention that, i'm using Debian stable with i3.

sgosnell · 10-03-2020, 02:57 PM

What desktop environment? Those tend to have their own method of controlling the keyboard, so the exact setting method varies by DE. I usually run Xfce, but sometimes KDE. I'm not familiar enough with the others to tell you how to go about changing the settings in those.

earthw0rmjim · 10-03-2020, 03:30 PM

I've edited my original post with the distro/de.
I think all desktop environments use (more or less) the same ways under the hood to control the backlight.
In my case i cannot even find a trace of my kernel recognizing the backlit keyboard. I guess there should be something in /sys/class/leds, /sys/class/backlight or /proc/acpi, but i find nothing.

EDIT: Found the following:

Code:

$ cat /proc/bus/input/devices

I: Bus=0011 Vendor=0001 Product=0001 Version=ab83
N: Name="AT Translated Set 2 keyboard"
P: Phys=isa0060/serio0/input0
S: Sysfs=/devices/platform/i8042/serio0/input/input0
U: Uniq=
H: Handlers=sysrq kbd leds event0 
B: PROP=0
B: EV=120013
B: KEY=402000000 3803078f800d001 feffffdfffefffff fffffffffffffffe
B: MSC=10
B: LED=7

Can i use this information somehow?

sgosnell · 10-03-2020, 04:22 PM

Perhaps. You still didn't say what desktop environment you're using, though. For instance, Xfce uses an applet to set this.

I did stumble on one possibility. I don't have a laptop with backlit keyboard, but there is a file /sys/class/backlight/acpi_video0/bl_power. The sole contents are the number 0. I suspect it's a binary 0 or 1, and may control the backlighting. I have no way of testing this. The subdirectory under sys/class/backlight might be different depending on the hardware installed. Perhaps changing yours to 0 would turn the backlight off, but again, I have not tested this. Better to run the applet in your DE, whatever it is - gnome, mate, cinnamon, KDE, Xfce, LXDE, or whatever. There are other files in my system, but I haven't investigated them. It might be a starting point.

BTW, there are many apps available on GitHub that control backlit keyboards. Again, no recommendations because I've never tried any of them.