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Keyboard Backlight on a 2011 Macbook

Specs:
Artix runit LXQt
Late 2011 Macbook Pro 13"

My keyboard backlight is not working. Previously I had endeavourOS installed and it worked out of the box so I'm not sure what to do. I installed xorg-xbacklight and it does nothing, and gives me an error when using -inc parameter without sudo:
/usr/bin/xbacklight: [Errno 13] Permission denied: '/sys/class/leds/input10::capslock/brightness'
 
I tried following this guide:
https://wiki.archlinux.org/title/MacBookPro8,1/8,2/8,3_(2011)
And it says:
"Adjust Brightness: works with xorg-xbacklight"
"Note: Since Linux kernel 6.1, an additional backlight kernel parameter is needed such as acpi_backlight=native."
So this was my next step:
https://wiki.archlinux.org/title/Kernel_parameters
I'm not sure what to do here because it seems to be based on systemd and I don't want to do anything I'll regret. I'm not sure if I'm on the right track either. Thanks for any help.

Re: Keyboard Backlight on a 2011 Macbook

Reply #1 –
It sounds like you are on the right track.
Quote
"Note: Since Linux kernel 6.1, an additional backlight kernel parameter is needed such as acpi_backlight=native."
From here https://wiki.archlinux.org/title/Backlight#Kernel_command-line_options these are the options available.
Code: [Select]
acpi_backlight=video
acpi_backlight=vendor
acpi_backlight=native
I'm not sure which would be the correct option for you so you'll have to try them one by one until one hopefully works.
Assuming you use grub as a bootloader you can easily add a kernel parameter by editing /etc/default/grub
https://wiki.archlinux.org/title/Kernel_parameters#GRUB
Add your parameter,  re-generate the grub.cfg, reboot. If it works great, if not try again with the next parameter.
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Re: Keyboard Backlight on a 2011 Macbook

Reply #2 –
Thank you for the help. I have tried editing /etc/default/grub to include each parameter one at a time:
acpi_backlight=video
acpi_backlight=vendor
acpi_backlight=native

None of them worked. I made sure to re-generate grub.cfg each time before rebooting, and tried using xbacklight to test on reboot.

Re: Keyboard Backlight on a 2011 Macbook

Reply #3 –
The output of
Code: [Select]
sudo dmesg
might show something ?
But also look at dmesg yourself with each of the kernel parameters, are there differences?
Quote
"Note: Since Linux kernel 6.1, an additional backlight kernel parameter is needed such as acpi_backlight=native."
I'd be interested to see if an older kernel fixed your issue? If not the acpi_backlight parameter, while probably still needed on the current kernel, won't fix the underlying problem, whatever that is?

Re: Keyboard Backlight on a 2011 Macbook

Reply #4 –
I have searched through the output of dmesg and found nothing relating to "backlight" or "acpi_backlight"  except for this line:
Code: [Select]
[   13.376415] i915 0000:00:02.0: [drm] Skipping intel_backlight registration

I noticed the keyboard is input9 here:
Code: [Select]
[    1.535485] input: Apple Inc. Apple Internal Keyboard / Trackpad as /devices/pci0000:00/0000:00:1a.7/usb1/1-1/1-1.2/1-1.2:1.0/0003:05AC:0252.0003/input/input9
This matches the error message I got using xbacklight.

I also noticed some warnings relating to acpi:
Code: [Select]
...
[   12.461256] ACPI: Smart Battery System [SBS0]: Battery Slot [BAT0] (battery present)
[   12.474253] mc: Linux media interface: v0.10
[   12.482975] ACPI: bus type thunderbolt registered
[   12.492793] ACPI Warning: SystemIO range 0x0000000000000428-0x000000000000042F conflicts with OpRegion 0x0000000000000400-0x000000000000047F (\PMIO) (20220331/utaddress-204)
[   12.492804] ACPI: OSL: Resource conflict; ACPI support missing from driver?
[   12.492808] ACPI Warning: SystemIO range 0x0000000000000540-0x000000000000054F conflicts with OpRegion 0x0000000000000500-0x0000000000000563 (\GPIO) (20220331/utaddress-204)
[   12.492813] ACPI: OSL: Resource conflict; ACPI support missing from driver?
[   12.492815] ACPI Warning: SystemIO range 0x0000000000000530-0x000000000000053F conflicts with OpRegion 0x0000000000000500-0x0000000000000563 (\GPIO) (20220331/utaddress-204)
[   12.492819] ACPI: OSL: Resource conflict; ACPI support missing from driver?
[   12.492821] ACPI Warning: SystemIO range 0x0000000000000500-0x000000000000052F conflicts with OpRegion 0x0000000000000500-0x0000000000000563 (\GPIO) (20220331/utaddress-204)
[   12.492825] ACPI: OSL: Resource conflict; ACPI support missing from driver?
[   12.492826] lpc_ich: Resource conflict(s) found affecting gpio_ich
[   12.503534] mousedev: PS/2 mouse device common for all mice
...

I didn't notice any differences when changing acpi_backlight.
 

Re: Keyboard Backlight on a 2011 Macbook

Reply #6 –
As you stated earlier that you tried as a kernel loading option:
Code: [Select]
acpi_backlight=vendor
My research showed the 2011 MacBook Pro back light required that line to function though the website pages are from 2012 time frame.
A complete post of the "dmesg" may helpful with the various kernel options if you want more forum help.