More than a few weeks ago, I updated to the Linux kernel 7.1 (from 6.18.x), as a flimsy attempt to solve an unrelated wifi issue (it didn’t solve the wifi issue, haha).
Everything was fine except I noticed that I couldn’t change my screen brightness any more. I can adjust it up and down, but the screen’s brightness actually doesn’t change. I figured this regression would resolve eventually, but I got kinda annoyed and decided to try rolling down to Linux kernel 7.0 instead.
Rolling down to Linux 7.0 restored the screen brightness controls, yay!
Today, however, Manjaro’s rolling update came through and upgraded my kernel to Linux 7.1… I looked at that update and hoped that the screen brightness regression had been resolved but…nope!
So here we are! Manjaro Linux 7.1 and I can only use a phantom brightness control. Weird thing though…I can’t seem to find any other complaints about this on the internet, so I figured I’d start a thread here (given I’m using Manjaro), and hopefully the solution to this regression will emerge.
Does anybody know if the kernel changed something fundamental to the screen brightness, like introducing a new software switch? For example, this fedora post makes me wonder if it’s addressing the same problem, but grubby isn’t a Manjaro thing, and I’m not even sure if acpi_backlight=native is a MacBook thing.
Finding a solution is preferable to the workaround I’ve discovered:
Temporary workaround:
I mentioned the phantom brightness control… so I can adjust the brightness from 0% to 100% and nothing happens, but as I workaround I found that if I dim my ceiling light whilst adjusting the screen brightness higher, it seems like the MacBook’s screen brightness is increasing.
Furthermore, if I reverse my room’s dimmer to make the ceiling light brighter, whilst lowering the screen brightness, it seems like the MacBook’s screen brightness is decreasing.
I hold no responsibility to the risk of your sanity if you choose to use this workaround.
I’ve had issues with HWE (mainline) kernels before; in my case the trackpad not working (reliably). How well does it work with an LTS kernel e.g. linux618? If that works, I’d suggest staying with the LTS series.
It might also help if you provide the output of inxi -zv8.
It works fine on the LTS kernel (linux618), and it also works fine on linux70.
Of course, I could roll back, but the main problem is that this issue has emerged with linux71 and nobody seems to be talking about it… so hopefully people will be able to find this forum thread when seeking the solution.
I haven’t tried linux72 yet, which might have fixed the problem, perhaps I should give that a try…
New information: I’ve just discovered that the display doesn’t turn off when I close the lid, either (as per my configuration). So the backlight just stays on keeping my keyboard cosy and warm. I guess this means that the backlight is usually turned off through a brightness=0% mechanism, rather than a backlight=disable mechanism, when closing the lid.
I tried installing linux72 (7.2.0-rc2-1-MANJARO), and the issue persists with linux72 as well. So the regression is introduced in linux71 and persists in linux72.
So here’s the wild thing… linux70 is no longer an option for me to roll back to, so weird!
From here, I was able to downgrade back to Linux 7.0.13:
❯ sudo pacman -U /var/cache/pacman/pkg/linux70-7.0.13-1-x86_64.pkg.tar.zst /var/cache/pacman/pkg/linux70-headers-7.0.13-1-x86_64.pkg.tar.zst
loading packages...
resolving dependencies...
looking for conflicting packages...
:: linux70-headers-7.0.13-1 and linux-headers-meta-7.1-1 are in conflict. Remove linux-headers-meta? [y/N] y
:: linux70-7.0.13-1 and linux-meta-7.1-1 are in conflict. Remove linux-meta? [y/N] y
As you can see from the last two lines, I had to remove the conflicting linux-meta packages. Hooray!
I’m not sure if pacman also updates the grub when installing a new kernel, but I did this anyway just in case:
I can’t find the article right now but I read in the last week something about Kernel 7.2 (I think - it may have been KDE 6.8) including some driver or change that is like adaptive brightness that hasn’t been enabled until now.
I know you weren’t on 7.2 but perhaps it was a related change as I’m pretty sure it related to Mac machines.
The lid not turning off is actually the bigger clue here imo — that plus the brightness tells you it’s probably an ACPI or power management thing, not just a backlight driver tweak. Might be worth checking if there’s a new acpi_* kernel param you need to set, or if something in your firmware changed. And yeah, 7.2 would be worth testing if you have time, just to see if the earlier changes they mentioned actually landed a fix.
