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Author Topic: Easy backlighting  (Read 3656 times)

Offline PDP-8

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Easy backlighting
« on: August 05, 2019, 08:48:06 PM »
Found something to try on netbooks / laptops etc that may rely a lot on acpi.

At least on my old Compaq Presario CQ60 laptop, to get the backlighting function keys to work, it was as simple as adding this to my boot line:

Code: [Select]
acpi_osi=Linux  acpi_backlight=vendor
Nah, can't be that easy really?  At least on this machine it is.  wow.  No guarantees on your box, but worth a shot.

That's a UNIX book! - cool  -- Garth

Offline Juanito

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Re: Easy backlighting
« Reply #1 on: August 06, 2019, 03:18:23 AM »
This does not work for me.

On my hardware - dell laptop, intel graphics - loading graphics-KERNEL is what creates the following (with or without the boot codes):
Code: [Select]
$ ls /sys/class/backlight/intel_backlight
actual_brightness  device             subsystem
bl_power           max_brightness     type
brightness         power/             uevent

..but even with xf86-video-intel loaded and the following:
Code: [Select]
$ grep back /var/log/Xorg.0.log
[  3862.009] (**) intel(0): Found backlight control interface intel_backlight (type 'raw') for output eDP1
..the backlight function keys do not work. I can however change the brightness from the cli.

Offline Juanito

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Re: Easy backlighting
« Reply #2 on: August 06, 2019, 03:28:05 AM »
The backlight function keys do work in the gnome environment (using gnome-session and wayland) without any configuration.

Offline PDP-8

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Re: Easy backlighting
« Reply #3 on: August 06, 2019, 04:38:36 AM »
Glad you brought that up.

This solution that worked on my old laptop can be hit-and-miss on other machines because the whole OSI thing is a total joke and misused often:

https://www.kernel.org/doc/html/latest/firmware-guide/acpi/osi.html

Perhaps see if only using acpi_backlight=vendor, and NOT using the osi=Linux cheat makes any difference?

Heh, where's my old IMSAI where none of this was a problem! :)
That's a UNIX book! - cool  -- Garth