No display brightness control in Gnome

[bkarlan]

Oddly, there is a control for the keyboard brightness in Power, but nowhere is there a way to adjust my brightness settings for my 2 27" Thunderbolt Monitors. Not even my keyboard button has any effect.

[Yochanan]

Please post your system info as outlined here:

How to provide good information

When asking questions in the forum it is most helpful to everyone for you to provide some basic information. When sharing information to either give or receive assistance, please be aware of the following: 1 ) In almost every situation not explicitly involving appearance, Text is preferred over Images. 2 ) When providing code or text output, please format it so the content is easy to read. How to Format “Code” in the Forum Its easy to make your text and code easy on the eyes Firs…

Also please post the output of the following:

ls /sys/class/backlight/

Now replace < result > in the next command with the output of the previous command:

ls /sys/class/backlight/< result >

[bkarlan]

@Yochanan

ls /sys/class/backlight/

Before I do that, I noticed that in laptop mode, the brightness adjustments work fine and the slider is there in the power section. It’s just not working in clamshell mode. I have an early 2013 MB Pro Retina, 15" 2.7Ghz i7 with 16GB RAM and 1TB SSD. Additionally, if I open the laptop and have a third screen the screen brightness can be changed, but only on the laptop screen not on the 2 thunderbolt monitors.

In regards to your outputs, they are the following:
gmux_backlight
&
actual_brightness brightness max_brightness scale type
bl_power device power subsystem uevent

[nazibalalam]

@bkarlan

It’s just not working in clamshell mode.

@bkarlan

Additionally, if I open the laptop and have a third screen the screen brightness can be changed, but only on the laptop screen not on the 2 thunderbolt monitors.

I would just try adjusting the brightness from the buttons of the monitor(s). The brightness buttons don’t work on my windows laptop. So I would only think how less support they would have on a linux laptop.

@bkarlan

but only on the laptop screen not on the 2 thunderbolt monitors.

Additionally, I wouldn’t use a thunderbolt for monitor(s). But the built-in HDMI cables on laptop(s). They prove better performance and compatibility for monitor(s) as compared to thunderbolt(s).

[bkarlan]

I’m on a MacBook Pro, thunderbolt is my only option. There are no buttons to adjust the brightness.