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

[1fallen]

I can't vote for it, it's not happening on mine.
It dose not seem to gather any interest in fixing it.
But your convinced it's not a keyboard driver so I'll just watch from the sidelines.

If it was me I'd file it on ACPI.
Just trying to help.

[MAFoElffen]

The setting is under the brightness file under the (simulated) /sys/class/backlight/acpi_X... Which that folder is really a symlink, which points /sys/devices/<Bus>/<slot, etc>/acpi_videoX/

Here is something to try. (Is not persistent...) You need to be root, because of the permissions on the settings file...

sudo su -
Paths=$(find /sys/devices/*/*/ -name acpi_video* 2>/dev/null) && for Path in ${Paths}; do grep . $Path/brightness; done

It will output what the brightness settings current are... Lets say it says "15". "12" would be about 75% of that right?

for Path in ${Paths}; do sudo echo "12" > $Path/brightness; done

Play with it, and see if it changes anything for you...

[dragonfly41]

I know very little on this subject to help but what I tend to do when I'm stuck is grab the evidence as written in your bug report and submit a Query to a Chat GPT assistant - Phind.com in my case - to let it do more detective work. Unfortunately the reply is submit a bug report. But this workaround is mentioned.

• Use xcalib: Another workaround involves using the xcalib tool, which can adjust the screen brightness if your video card supports the relevant extension. To test if xcalib works on your machine, you can install it and run xcalib -i -a. If this command inverts the colors on your screen, it means xcalib is working. To revert back to your original screen, run the command again. Then, you can configure xcalib to adjust the brightness 5.

sudo apt install xcalib
xcalib -i -a

[ne29914]

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

No. I don't even remember my GitLab login. And I'm not going back to the top "User-Hating" thing I've ever experienced.
It's probably good for developers, but NOT for users.
You will get zero votes. No user logs in unless it's a masochist.
If you're really lucky, a developer might have the same issue and give you a vote, but don't hold your breath.

[Paddy Landau]

But your convinced it's not a keyboard driver so I'll just watch from the sidelines.

I'm unsure how it could be a keyboard driver, because it's not related to any keystrokes? Or is the keyboard driver somehow related to the monitor brightness settings? If I can change the brightness with xrandr, that's nothing to do with the keyboard, right?

If it was me I'd file it on ACPI.

Do you mean on Launchpad against ACPI? Or is there some other place where I should report it? Sorry, I'm rather ignorant in these matters.

sudo su - …

For me, I get zero results with this:

sudo su
find /sys/devices/*/*/ -name 'acpi_video*'

… xcalib …

Well, xcalib does work on my machine. But, I didn't understand how to amend the brightness. In the end, trying to amend the brightness got me into a spot of trouble — I had to reboot the machine because I couldn't see what I was doing, ha ha! I'll stick with xrandr.

No. I don't even remember my GitLab login. And I'm not going back to the top "User-Hating" thing I've ever experienced.
It's probably good for developers, but NOT for users.
You will get zero votes. No user logs in unless it's a masochist.
If you're really lucky, a developer might have the same issue and give you a vote, but don't hold your breath.

This isn't GitLab; it's Ubuntu's Launchpad. I've issued plenty of bugs on Launchpad, and many of them have been addressed and fixed. There's no "user-hating", which fortunately for me, I don't think that I've ever experienced. Certainly never on Launchpad.

But, I need someone to vote for the bug report, because when you get zero votes, it's automatically closed after a while. If you could please vote for it — that's all you have to do, there's no "user-hating" — then at least someone will start to look at it. If it's not suitable for Launchpad, someone will tell me where to repost the bug — but that won't happen without a vote! (You log into Launchpad with the same ID that you use to log into Ubuntu Forums; you don't have to create a new account.) Thank you

[MAFoElffen]

I looked back at your first post to see which computer is was, then did a bit of digging...

Kernel module 'dell_uart_backlight' is responsible for controlling the brightness on that. When there is a problem with that, then the brightness control widget can disappear or not work correctly... They started having problems with Mantic, which uses Kernel 6.5 (https://askubuntu.com/questions/1491...in-computer-de) Jammy 22.04.3 last week just went to kernel 6.5.0-14.

The User found that if he booted with one of the 6.2.0-X kernels, it then worked again. So the problem is related to Linux kernel 6.5.0-14...

Digging deeper, I found this Bug Report which affected module 'dell_uart_backlight' related to 6.5.0: https://bugs.launchpad.net/ubuntu/+s...x/+bug/2032174

You can see that one that Bug Report, the fix was patched for Mantic, in source package 'linux-oem-6.5'. At the time, Jammy wasn't running kernel 6.5... But it did say that fixes where applied to jammy for both 'linux' and linux-oem-6.5'...

I would file your bug at LaunchPad, using the "Report a Bug" link in the upper right of that page, against 'linux' and 'linux-oem-6.5'.

I might also use find, to look to see if the kernel module 'dell-uart-backlight.ko' is in the modules directory in the 6.5.0 kernel tree

find /lib/modules -name dell-uart-backlight.ko

I can see it built on mine, but cannot confirm that it is working (on machines I have 6.5.0-14 still installed), as I don't have any Dell's here.

Me??? I'm having problem with Linux Kernel 6.5.0-14 also... But on NVidia drivers not building modules for that kernel in Jammy. That kernel is also affecting some users using VirtualBox from the repo's for Jammy.

[Paddy Landau]

I looked back at your first post to see which computer is was, then did a bit of digging...

Thank you! You found much more than I did. Thank you for the links.

The User found that if he booted with one of the 6.2.0-X kernels, it then worked again. So the problem is related to Linux kernel 6.5.0-14...

This is exactly what I found, which I've mentioned in my bug report (as noted below).

I would file your bug at LaunchPad, using the "Report a Bug" link in the upper right of that page, against 'linux' and 'linux-oem-6.5'.

Thanks, I have done this.

I might also use find, to look to see if the kernel module 'dell_uart_backlight' is in the modules directory in the 6.5.0 kernel tree

This, unfortunately, gave zero results:

find /lib/modules -name dell_uart_backlight*

Me??? I'm having problem with Linux Kernel 6.5.0-14 also... But on NVidia driver not building modules for that kernel in Jammy. That kernel is also affecting some users usig VirtialBox from the repo's for Jammy.

Do you think that this is related?

[MAFoElffen]

Yours is Intel UHD 6XX graphics right?

[Paddy Landau]

Yours is Intel UHD 6XX graphics right?

You seem to have duplicated most of your previous post!

To answer your question, I don't know how to tell, but I tried this:

$ sudo lshw -numeric -C display
  *-display                 
       description: VGA compatible controller
       product: CometLake-S GT2 [UHD Graphics 630] [8086:9BC5]
       vendor: Intel Corporation [8086]
       physical id: 2
       bus info: pci@0000:00:02.0
       logical name: /dev/fb0
       version: 05
       width: 64 bits
       clock: 33MHz
       capabilities: pciexpress msi pm vga_controller bus_master cap_list rom fb
       configuration: depth=32 driver=i915 latency=0 resolution=1920,1080
       resources: irq:145 memory:c1000000-c1ffffff memory:d0000000-dfffffff ioport:3000(size=64) memory:c0000-dffff

Does that answer your question, or do I have to look elsewhere?

EDIT: Oh, wait, the answer is yes!

[MAFoElffen]

LOL. Dang. Didn't notice I had double posted...

Here is what I have with that (and I don't even have Dell):

mafoelffen@Mikes-B460M:~$ find /lib/modules -name dell-uart-backlight.ko
/lib/modules/6.5.0-14-generic/kernel/drivers/platform/x86/dell/dell-uart-backlight.ko
/lib/modules/6.2.0-39-generic/kernel/drivers/platform/x86/dell/dell-uart-backlight.ko

But that one does have

mafoelffen@Mikes-B460M:~$ lspci -nnnk | grep -A3 -E 'Display|VGA|3D'
00:02.0 VGA compatible controller [0300]: Intel Corporation CometLake-S GT2 [UHD Graphics 630] [8086:9bc5] (rev 05)
    DeviceName: Onboard - Video
    Subsystem: Gigabyte Technology Co., Ltd CometLake-S GT2 [UHD Graphics 630] [1458:d000]
    Kernel driver in use: i915