Hi,
I have exact same issue on my MacBook Pro (mid-2014) - slider is moving on screen when pressing brightness buttons, but actual brightness does not change.
I tried all I could find regarding this (installing xbacklight, powertop, changing boot options) - but none worked.
Are there any fresh ideas about this?
It is small issue, but really annoying in evening / night hours.
Thanks,
Mario

I also have an older macbook pro, and had the same issue. I solved it by installing powertop. Not sure why it fixed it, but... might be worth trying?

    linny as I mentioned, I did try installing power top, but nothing changed.

      whoops I guess I missed that in your comment above. 🙁 I don't really know why it's not working for you. Pretty frustrating for sure. Hope you figure it out. I think this is specifically a Mac/Solus issue.

      25 days later

      linny Surprise!!! I also have problem with function key fn+f4/f5 to adjust my backlight, but this problem just knock on me when i am playing media in Firefox like music, video, so weird @_@. I can use function key, but when i press fn+f4/f5 one time, slide bar suddenly go down/up continuously until it reach limit and i can't do anything but see it automatic changes itself. Others place backlight fn+f4/f5 work fine, except website has media in Firefox ?!? Before i see this bug has happened in Ubuntu lts 18.4 (but in almost places), but i can fix by switch session to Wayland. But Solus doesn't offer this option yet. Oh wait...i'm using Solus Plasma up to date.

        linny I have installed xbacklight, powertop, but neither of them work for me. And sometime after bug i hit a whole system freezes that i can't do anything (include open up Terminal using Ctrl+alt+f2) except a force shutdown by press power button. Very annoying.

          This maybe goes without saying, but for the people who haven't gotten xbacklight to work, what command are you calling for the keyboard shortcut? Maybe something like this

          exec xbacklight -inc 5
          exec xbacklight -dec 5

          The solution is invariably a simple command pushed to grub in order get your bios to play nice with the gui & Fn buttons, but the exact command depends on your hardware. If you've got Intel graphics, a Lenovo, or the like, try the following, which works 99% of the time when 'acpi_osi=Linux' does not:

          Open Terminal,

          sudo echo 'acpi_backlight=none' | sudo tee /etc/kernel/cmdline

          sudo clr-boot-manager update

          Reboot.

            a month later
            4 months later
            10 months later

            JohannPopper just installed solus budgie today on panasonic cfc2 with intel graphics . I'm getting this error on with your fix " tee: /etc/kernel/cmdline: No such file or directory " TIA btw this OS is amazing hope to fix this and a audio issue

                • [deleted]

                • Post #18

                If you don't get the FN keys working, you can try my brightness app. It uses xrandr to control the brightness of the display(s). The app has an icon in the tray from where you control the brightness of all your displays, also simultaneously.


                • jamZ replied to this.

                  jamZ You get this message, because you don't have a directory called kernel located in /etc/.

                  You need to create this directory sudo mkdir /etc/kernel

                  After you do this, the command posted above by JohannPopper will work.

                  sudo echo 'acpi_backlight=none' | sudo tee /etc/kernel/cmdline

                  • jamZ replied to this.

                      Junglist thank you friend, i initially installed the MATE DE and the problem resolved itself somehow. After this i decided to give KDE(fresh reinstalled i heard it is not supported to migrate) a try and backlight worked out of the box. For some reason it stopped working again 🙁 i just ran this fix and it executed fine, rebooted and still no backlight control. I'm kind of a beginner to maybe intermediate linux guy so I'm sure I'm overlooking something basic. I went to see the app on github [deleted] but I don't understand how to install it. I do want the app even for a fallback if i get my FN keys working. TIA for any other pointers. this community seems real nice. think this diseased distro hopper finally found a OS to stick with.

                            a year later

                            JohannPopper
                            For me it didn't work 😢
                            Thanks for trying tho!

                            To be fair, I got an HP with AMD A9 & Stoney graphics, but yeah, I tried because I'm clueless what else to do 😓