I've lost the ability to change the brightness of my monitor

[Paddy Landau]

Up until a few minutes ago, when I ran the standard updates, I could adjust the brightness of my monitor either from the settings or via the keyboard shortcuts.

Now, the monitor is set to maximum brightness, which is so bright that it hurts my eyes. The keyboard shortcuts do nothing; and Settings > Screen Display no longer displays a brightness bar.

I can change the brightness using xrandr, but after a while, the monitor resets back to full brightness all by itself! The time before it resets varies seemingly arbitrarily from a couple of seconds to a few minutes.

xrandr --current                         # Tells me that the monitor name is eDP-1.
xrandr --output eDP-1 --brightness 0.5   # Sets brightness to 50%, for a short while only.

I have no clue how to diagnose or fix this. I don't know what apps were updated when I ran the updates a few minutes ago, nor how to find out.

• Hardware: Dell OptiPlex 5480 All-In-One
• Ubuntu 22.04
• This problem is happening on both Wayland and X.Org (I usually use X.Org)

Are you able to help, please?

[dragonfly41]

Some repeat stories here ..

https://duckduckgo.com/?q=ubuntu+22....nonical&ia=web

Perhaps glean a few clues.

[tea for one]

A new kernel arrived today (10 January 2024) - vmlinuz-6.5.0-14-generic.
Perhaps try an earlier kernel and see if equilibrium is restored.

[#&thj^%]

Paddy dose this show anything?

journalctl -f | grep 'gnome-shell.*Soft-Brightness'

[Paddy Landau]

Some repeat stories here ..

Thanks, but they seem to be to do with Nvidia, which I don't have, and they don't address this continuous resetting of the brightness.

Paddy dose this show anything?

journalctl -f | grep 'gnome-shell.*Soft-Brightness'

Unfortunately, nothing at all. Even when I manually reduce the brightness, and the system automatically makes it 100% again, it still shows nothing.

A new kernel arrived today (10 January 2024) - vmlinuz-6.5.0-14-generic.
Perhaps try an earlier kernel and see if equilibrium is restored.

This is the one that worked, thank you. I rebooted, and chose the previous version (6.2.0-39) from Grub. This restored the full brightness control. When I rebooted again into the new kernel, the problem resurfaced.

(As a side-note, my laptop works fine with the new kernel.)

This is, therefore, clearly a bug relating to the new kernel.

How specifically should I report this? On Launchpad, I imagine? Also, what hardware information would I need to include? Perhaps the GPU?

sudo lshw -numeric -C display

[#&thj^%]

Paddy i would think it would be "ACPI"
ACPI is a power interface management standard which is implemented in operating system kernels. By default Linux kernel uses an inbuilt driver for keyboard keys, which is often non compatible with some keyboards.

[ne29914]

Old story, but never solved. No one cares about this.
That's why I'm still on 20.04. 22.04 killed the brightness function. Reported to GitLab, dead after the default 90 days.
Oh. well...

[Paddy Landau]

Paddy i would think it would be "ACPI"
ACPI is a power interface management standard which is implemented in operating system kernels. By default Linux kernel uses an inbuilt driver for keyboard keys, which is often non compatible with some keyboards.

Thanks, but it's not the keyboard at fault. It's the brightness itself.

22.04 killed the brightness function.

It worked on my 22.04 until the latest kernel update. So, I wonder if it's something to do with the kernel and hardware rather than Ubuntu?

Reported to GitLab, dead after the default 90 days.

Would you give me the link, please, so that I can refer to it when I create a bug report? I'll link my report here once done so that you can vote for it.

[ne29914]

Would you give me the link, please, so that I can refer to it when I create a bug report? I'll link my report here once done so that you can vote for it.

Mine's so old, I abandoned it.

Just submit your report. If you're lucky, someone will respond with "not able to reproduce the issue" and ask for more info.
Then silence, and you can watch it expire after 90 days.

[Paddy Landau]

Mine's so old, I abandoned it.

It would be interesting to see where you reported it, so if you have the link, please let me know.

Anyway, I've submitted the bug report.

Please vote for it (log in, and select the green writing near the top left).