Manjaro KDE Kernel 5.10 Adjust Brightness on 2015 iMac


The brightness adjustment doesn’t work on 2015 iMac, there is no error messages,
just nothing happened when I adjusted the brightness, the screen stays at the
brightest level all the time. I tested Kernel 5.4, no issues with brightness adjustment.

I also tested on my 2015 MacBook Pro, brightness works fine with both Kernel 5.4
and Kernel 5.10


Additional information (iMac running Kernel 5.10):

result of “echo 10 | sudo tee /sys/class/backlight/acpi_video0/brightness”:

result of “echo 10 | sudo tee /sys/class/backlight/acpi_video0/brightness”

Finally, result of “inxi --admin --verbosity=7 --filter --no-host --width” :

Kernel: 5.10.34-1-MANJARO x86_64 bits: 64 compiler: gcc v: 10.2.0
parameters: BOOT_IMAGE=/boot/vmlinuz-x86_64 lang=en_US keytable=us tz=UTC
misobasedir=manjaro misolabel=MANJARO_KDE_2104 quiet systemd.show_status=1
apparmor=1 security=apparmor driver=nonfree nouveau.modeset=0 i915.modeset=1
Desktop: KDE Plasma 5.21.4 tk: Qt 5.15.2 wm: kwin_x11 vt: 1 dm: SDDM
Distro: Manjaro Linux base: Arch Linux
Type: Desktop System: Apple product: iMac14,3 v: 1.0 serial:
Chassis: type: 13 v: Mac-77EB7D7DAF985301 serial:
Mobo: Apple model: Mac-77EB7D7DAF985301 v: iMac14,3 serial:
UEFI: Apple v: IM143.88Z.0129.B00.1802091637 date: 02/09/2018
Message: No system battery data found. Is one present?
RAM: total: 7.71 GiB used: 4.35 GiB (56.4%)
Array-1: capacity: 8 GiB slots: 2 EC: None max-module-size: 4 GiB note: est.
Device-1: DIMM0 size: 4 GiB speed: 1600 MT/s type: DDR3 detail: synchronous
bus-width: Unknown total: Unknown manufacturer: 0x02FE
part-no: 0x45424A3430554738454655352D474E4C2D46 serial:
Device-2: DIMM0 size: 4 GiB speed: 1600 MT/s type: DDR3 detail: synchronous
bus-width: Unknown total: Unknown manufacturer: 0x02FE
part-no: 0x45424A3430554738454655352D474E4C2D46 serial:
Info: Quad Core model: Intel Core i5-4570S socket: LGA1150 (U3E1)
note: check bits: 64 type: MCP arch: Haswell family: 6 model-id: 3C (60)
stepping: 3 microcode: 28 cache: L1: 256 KiB L2: 6 MiB L3: 6 MiB
bogomips: 23148
Speed: 2894 MHz min/max: 800/3600 MHz base/boost: 2900/2900 volts: 1.0 V
ext-clock: 25 MHz Core speeds (MHz): 1: 2894 2: 2895 3: 2894 4: 2894
Flags: abm acpi aes aperfmperf apic arat arch_perfmon avx avx2 bmi1 bmi2 bts
clflush cmov constant_tsc cpuid cpuid_fault cx16 cx8 de ds_cpl dtes64 dtherm
dts epb ept ept_ad erms est f16c flexpriority flush_l1d fma fpu fsgsbase
fxsr ht ibpb ibrs ida invpcid invpcid_single lahf_lm lm mca mce md_clear mmx
monitor movbe msr mtrr nonstop_tsc nopl nx pae pat pbe pcid pclmulqdq pdcm
pdpe1gb pebs pge pln pni popcnt pse pse36 pti pts rdrand rdtscp rep_good
sdbg sep smep smx ss ssbd sse sse2 sse4_1 sse4_2 ssse3 stibp syscall tm tm2
tpr_shadow tsc tsc_adjust tsc_deadline_timer vme vmx vnmi vpid x2apic xsave
xsaveopt xtopology xtpr
Vulnerabilities: Type: itlb_multihit status: KVM: VMX disabled
Type: l1tf
mitigation: PTE Inversion; VMX: conditional cache flushes, SMT disabled
Type: mds mitigation: Clear CPU buffers; SMT disabled
Type: meltdown mitigation: PTI
Type: spec_store_bypass
mitigation: Speculative Store Bypass disabled via prctl and seccomp
Type: spectre_v1
mitigation: usercopy/swapgs barriers and __user pointer sanitization
Type: spectre_v2 mitigation: Full generic retpoline, IBPB: conditional,
IBRS_FW, STIBP: disabled, RSB filling
Type: srbds mitigation: Microcode
Type: tsx_async_abort status: Not affected
Device-1: NVIDIA GK107M [GeForce GT 750M Mac Edition] vendor: Apple
driver: nvidia v: 390.143 alternate: nouveau,nvidia_drm bus-ID: 01:00.0
chip-ID: 10de:0fe9 class-ID: 0300
Device-2: Apple FaceTime HD Camera (Built-in) type: USB driver: uvcvideo
bus-ID: 1-7:5 chip-ID: 05ac:8511 class-ID: 0e02 serial:
Display: x11 server: X.Org 1.20.11 compositor: kwin_x11 driver:
loaded: nvidia display-ID: :0 screens: 1
Screen-1: 0 s-res: 4080x1920 s-dpi: 101 s-size: 1027x483mm (40.4x19.0")
s-diag: 1135mm (44.7")
Monitor-1: DP-2 res: 1920x1080 hz: 60 dpi: 103 size: 475x267mm (18.7x10.5")
diag: 545mm (21.5")
Monitor-2: DP-3 res: 1080x1920 hz: 60
Monitor-3: DP-4 res: 1080x1920 hz: 60
OpenGL: renderer: GeForce GT 750M/PCIe/SSE2 v: 4.6.0 NVIDIA 390.143
direct render: Yes
Device-1: Intel 8 Series/C220 Series High Definition Audio
driver: snd_hda_intel v: kernel bus-ID: 00:1b.0 chip-ID: 8086:8c20
class-ID: 0403
Device-2: NVIDIA GK107 HDMI Audio driver: snd_hda_intel v: kernel
bus-ID: 01:00.1 chip-ID: 10de:0e1b class-ID: 0403
Sound Server-1: ALSA v: k5.10.34-1-MANJARO running: yes
Sound Server-2: JACK v: 0.125.0 running: no
Sound Server-3: PulseAudio v: 14.2 running: yes
Sound Server-4: PipeWire v: 0.3.26 running: yes
Device-1: Broadcom BCM4360 802.11ac Wireless Network Adapter vendor: Apple
driver: bcma-pci-bridge v: N/A modules: bcma port: 1000 bus-ID: 03:00.0
chip-ID: 14e4:43a0 class-ID: 0280
Device-2: Broadcom NetXtreme BCM57766 Gigabit Ethernet PCIe driver: tg3
v: kernel port: 1000 bus-ID: 04:00.0 chip-ID: 14e4:1686 class-ID: 0200
IF: enp4s0f0 state: up speed: 100 Mbps duplex: full mac:
IP v4: [filter] type: dynamic noprefixroute scope: global
broadcast: [filter]
IP v6: [filter] type: dynamic noprefixroute scope: global
IP v6: [filter] type: noprefixroute scope: link
WAN IP: [filter]
Device-1: Apple Bluetooth USB Host Controller type: USB driver: btusb v: 0.8
bus-ID: 1-8.3:9 chip-ID: 05ac:828d class-ID: fe01
Report: rfkill ID: hci0 rfk-id: 0 state: up address: see --recommends
Message: No logical block device data found.
Message: No RAID data found.
Local Storage: total: 946.11 GiB used: 0 KiB (0.0%)
ID-1: /dev/sda maj-min: 8:0 vendor: Apple model: HDD HTS541010A9E662
size: 931.51 GiB block-size: physical: 4096 B logical: 512 B sata: 2.6
speed: 3.0 Gb/s rotation: 5400 rpm serial: rev: B5D0 temp: 49 C
scheme: GPT
SMART: yes state: enabled health: PASSED on: 3y 224d 19h cycles: 83126
ID-2: /dev/sdb maj-min: 8:16 type: USB vendor: Transcend
model: JetFlash Transcend 16GB size: 14.6 GiB block-size: physical: 512 B
logical: 512 B rotation: SSD serial: rev: 8.07 scheme: MBR
SMART Message: Unknown USB bridge. Flash drive/Unsupported enclosure?
Message: No optical or floppy data found.
Message: No partition data found.
Alert: No swap data was found.
ID-1: /dev/sda1 maj-min: 8:1 size: 200 MiB fs: vfat label: EFI
uuid: 2860-11F4
ID-2: /dev/sda2 maj-min: 8:2 size: 180.45 GiB fs: hfsplus
label: Macintosh HD uuid: b7b100de-cd8f-3725-ae7a-7958a1391326
ID-3: /dev/sda3 maj-min: 8:3 size: 510.34 GiB fs: vfat label: M
uuid: 9783-1DEE
ID-4: /dev/sda4 maj-min: 8:4 size: 7.28 GiB fs: hfsplus label: Recovery HD
uuid: 430cd6e3-0b0f-33a6-88a5-bf517ffb2f5e
ID-5: /dev/sda5 maj-min: 8:5 size: 232.75 GiB fs: ext4 label: N/A
uuid: 42b859a9-34e7-4892-877f-f5e34f4410cb
ID-6: /dev/sdb1 maj-min: 8:17 size: 2.68 GiB fs: iso9660
label: MANJARO_KDE_2104 uuid: 2021-05-06-11-23-16-00
ID-7: /dev/sdb2 maj-min: 8:18 size: 4 MiB fs: vfat label: MISO_EFI
uuid: D498-2CF7
Hub-1: 1-0:1 info: Full speed (or root) Hub ports: 14 rev: 2.0
speed: 480 Mb/s chip-ID: 1d6b:0002 class-ID: 0900
Device-1: 1-1:2 info: Transcend Information JetFlash type: Mass Storage
driver: usb-storage interfaces: 1 rev: 2.0 speed: 480 Mb/s power: 200mA
chip-ID: 8564:1000 class-ID: 0806 serial:
Device-2: 1-2:3 info: Microsoft Natural Ergonomic Keyboard 4000 V1.0
type: Keyboard,HID driver: microsoft,usbhid interfaces: 2 rev: 2.0
speed: 1.5 Mb/s power: 100mA chip-ID: 045e:00db class-ID: 0300
Device-3: 1-6:4 info: Microsoft Comfort Mouse 4500 type: Mouse
driver: microsoft,usbhid interfaces: 1 rev: 2.0 speed: 1.5 Mb/s power: 100mA
chip-ID: 045e:076c class-ID: 0301
Device-4: 1-7:5 info: Apple FaceTime HD Camera (Built-in) type: Video
driver: uvcvideo interfaces: 3 rev: 2.0 speed: 480 Mb/s power: 500mA
chip-ID: 05ac:8511 class-ID: 0e02 serial:
Hub-2: 1-8:6
info: Broadcom BCM2046B1 USB 2.0 Hub (part of BCM2046 Bluetooth) ports: 3
rev: 2.0 speed: 12 Mb/s power: 94mA chip-ID: 0a5c:4500 class-ID: 0900
Device-1: 1-8.3:9 info: Apple Bluetooth USB Host Controller type: Bluetooth
driver: btusb interfaces: 4 rev: 2.0 speed: 12 Mb/s chip-ID: 05ac:828d
class-ID: fe01
Hub-3: 2-0:1 info: Full speed (or root) Hub ports: 6 rev: 3.0 speed: 5 Gb/s
chip-ID: 1d6b:0003 class-ID: 0900
System Temperatures: cpu: 71.0 C mobo: N/A gpu: nvidia temp: 77 C
Fan Speeds (RPM): N/A
Processes: 200 Uptime: 30m wakeups: 0 Init: systemd v: 247 tool: systemctl
Compilers: gcc: 10.2.0 Packages: pacman: 1222 lib: 326 flatpak: 0
Shell: Bash (su) v: 5.1.4 running-in: konsole inxi: 3.3.04