Linux kernel 7.1 rc 1 breaks display brightness control in Latitude E5450

Issues & Assistance
1

The slider and the keys don’t do anything.

2

I feel like you are just me a few months ago: installing a release candidate kernel and then making a topic on this forum about something being broken/not working correctly.

No distro will ever use release candidates for a reason, not even rolling release distros. Unlike Arch packages (which are just the latest normal release or something), release candidate are a beta-test in every meaning of the word. Don’t use it, some things just aren’t compatible with some system components/configurations.

3

I don’t think this is a kernel issue. I’m on the stock kernel, not the rc, and the slider and keys for brightness don’t do anything on my Dell Precision 7750 either.

4

Yes, I am aware that rc releases of kernels would be buggy, that’s why I put it under bug report.

5

It’s a regression for me, the stock kernel works fine.

6

I don’t see a particular reason why CachyOS devs should look at this

7

If nobody reports bugs with rc kernels then bugs will persist into the full release, and the devs will certainly be forced to look at them then. I’m pretty sure they would prefer at least a heads up, such as this post, so they can at least investigate and prepare fixes (or at least prepare warnings lol) before many more users hit issues.

8

I was thinking the same, I think he means that because its a kernel issue maybe the best place for it is the kernel bug report page…I’m not a developer so I figured I’d post it where I can so more eyes on it the sooner it being potentially fixed. Besides I think petr himself would like to provide good support for his users and might extend his hand here if he wishes to.

9

Also I want to add because I could not edit the post. I’ve found more bugs. The display does not power on after resuming the laptop from sleep/suspend. Gemini returned the below suggestion that I have not tried —–

”This combination of a non-functional backlight and a failure to wake from sleep (black screen on resume) strongly suggests a major regression in how the 7.1-rc1 kernel’s i915 driver is handling your Intel integrated graphics.

Since you are using Limine, you should try to stabilize the driver by adding specific workarounds to your cmdline.

1. The “Deep Sleep” Fix (Priority)

Modern Intel drivers use a feature called Panel Self Refresh (PSR) to save power, which is a notorious cause of “black screen on wake” issues.

  • Parameter: i915.enable_psr=0

  • Why: This disables the power-saving mode that often fails to re-initialize the display buffer when the system resumes .

2. Force Video Memory Preservati on

Sometimes the kernel fails to restore the video memory state after a suspend event, leading to a hard freeze or a black scre en.

  • Parameter: intel_idle.max_cstate=1

  • Why: This prevents the CPU from entering deep sleep states that might be interfering with the GPU’s ability to stay “awake” enough to handle the resume signal.

3. Update your Limine Config

To apply these, edit your /boot/limine.conf and update the cmdline for your 7.1 RC entry:

Plaintext

cmdline: root=UUID=... rw i915.enable_psr=0 i915.enable_dpcd_backlight=1
10

an update because I did not know where to mark it solves, this has been fixed since rc6. can be closed. thank you