HP Elitebook / Fedora 31 - brightness control function keys not working

[jacobyoby (Jacob)]

I have no idea where to start trouble shooting this issue. Below is some information about the system.

ls /sys/class/backlight/

> intel_backlight
> root@COVIDeezNutz ~]# inxi -F
> System:    Host: COVIDeezNutz.hsd1.wa.comcast.net Kernel: 5.5.10-200.fc31.x86_64 x86_64 bits: 64 Console: tty 0 
>        Distro: Fedora release 31 (Thirty One) 
> Machine:   Type: Laptop System: HP product: HP EliteBook 840 G6 v: N/A serial: 5CG9524PRP 
>        Mobo: HP model: 8549 v: KBC Version 52.58.00 serial: PHWHB00WBD63ET UEFI: HP v: R70 Ver. 01.04.02 date: 01/02/2020 
> Battery:   ID-1: BAT0 charge: 26.2 Wh condition: 49.2/49.2 Wh (100%) 
> CPU:       Topology: Quad Core model: Intel Core i7-8565U bits: 64 type: MT MCP L2 cache: 8192 KiB 
>        Speed: 800 MHz min/max: 400/4600 MHz Core speeds (MHz): 1: 634 2: 617 3: 622 4: 644 5: 638 6: 624 7: 618 8: 686 
> Graphics:  Device-1: Intel UHD Graphics 620 driver: i915 v: kernel 
>        Display: server: Fedora Project X.org 1.20.6 driver: i915 resolution: 1920x1080~60Hz 
>        OpenGL: renderer: Mesa DRI Intel UHD Graphics (Whiskey Lake 3x8 GT2) v: 4.5 Mesa 19.2.8 
> Audio:     Device-1: Intel Cannon Point-LP High Definition Audio driver: snd_hda_intel 
>        Sound Server: ALSA v: k5.5.10-200.fc31.x86_64 
> Network:   Device-1: Intel Ethernet I219-V driver: e1000e 
>        IF: enp0s31f6 state: down mac: e8:d8:d1:e6:ab:f6 
>        Device-2: Intel Wi-Fi 6 AX200 driver: iwlwifi 
>        IF: wlp58s0 state: up mac: 60:f2:62:4e:c2:cb 
>        IF-ID-1: virbr0 state: down mac: 52:54:00:42:4a:69 
>        IF-ID-2: virbr0-nic state: down mac: 52:54:00:42:4a:69 
> Drives:    Local Storage: total: 238.47 GiB used: 8.91 GiB (3.7%) 
>        ID-1: /dev/sda vendor: SanDisk model: SD9TN8W-256G-1006 size: 238.47 GiB 
> Partition: ID-1: / size: 61.70 GiB used: 7.89 GiB (12.8%) fs: ext4 dev: /dev/sda6 
>        ID-2: /boot size: 975.9 MiB used: 189.0 MiB (19.4%) fs: ext4 dev: /dev/sda4 
>        ID-3: /home size: 30.12 GiB used: 732.7 MiB (2.4%) fs: ext4 dev: /dev/sda7 
>        ID-4: swap-1 size: 7.71 GiB used: 0 KiB (0.0%) fs: swap dev: /dev/sda5 
> Sensors:   System Temperatures: cpu: 46.0 C mobo: 43.0 C 
>        Fan Speeds (RPM): N/A 
> Info:      Processes: 285 Uptime: 1h 25m Memory: 7.58 GiB used: 3.15 GiB (41.5%) Shell: bash inxi: 3.0.37 

[vits95 (Vitaliy Shatrov)]

Hi @jacobyoby.
There is some s*tty workaround with light;  use xbacklight for X-session.  It’s possibly not works for the external displays connected to laptops.

#! /bin/sh
# some "maded on the ankle" "solution"
# for ''intel_backlight''.
my_path=/sys/class/backlight/intel_backlight

if [[ ${1} == 'cat' ]];
        then
                # this part works for non-root
                echo "CUR Brightness: "\
                    `cat ${my_path}/brightness`
                echo "MAX Brightness: "\
                    `cat ${my_path}/max_brightness`

        # TODO: add a check if this is a number
        # root part, set brightness.
        else echo ${1} > ${my_path}/brightness;
fi
# light or xbacklight are better a lot.