Laptop backlight control regression with 465.24.02


BIOS 1.28 is the latest version for P17 Gen 1, P15 Gen 2 is still on 1.18. Updating sounds risky

indeed there is no update for P15 Gen 2. Do not update your system with the BIOS for the P15 Gen 1. It’s up to Lenovo to explain what they have modified in the P15 Gen 1 BIOS and if the Gen 2 series needs the same modifications.

There are users in this thread or other threads who confirmed that issue has been fixed.
But there are still few users who confirmed issue is not fixed for their system.
Please share acpi dump and bug report. either here or send to me personally.

acpidata.dat (1.7 MB)

I have a thinkpad P15 Gen 2, running ubuntu 22.04. T1200 Nvvidia graphics card with driver 510. I have no backlight control in discrete graphics mode and the laptop screen doesn’t load in hybrid graphics mode.

Thank you

I tried repro on ThinkPad-P1-Gen-3 laptop which has T1000 card; installed Ubuntu 20.04.3 LTS and driver 510.68.02 in discrete graphics mode but could not duplicate issue.
Shall try to find other lenovo systems and try to recreate issue locally.

1 Like

Thanks for looking into it

The bios version on the Gen 2 is 1.18

Hi! First, thank you for taking an interest in the problem.

As I posted before, I have the same issue with backlight control since 465 driver.

I’m using Clevo p775tm1 clone machine with single RTX 2080 mobile card.
For test purposes I’ve installed fresh Ubuntu 22.04, but problem appears at every linux distro.
I attach results of ‘ls /sys/class/backlight’, ‘inxi -Fxxi’, acpidump and bug report.

ls.txt (21 Bytes)
inxi.txt (4.1 KB)
acpidata.dat (876.9 KB)
nvidia-bug-report.log.gz (539.3 KB)

I can add, that only using acpi_backlight=video parameter I have apci_video0 and nvidia0 directories in /sys/class/backlight/. With vendor, native or none only nvidia0 appears. Video option also works with 460 and older. Now none of known solutions works (except of nvidia graphic driver downgrade or using nouveau).

Thanks for sharing data, we are trying to analyze issue based on attached logs since I do not have local repro.
I am trying to find similar model Clevo p775tm1 and attempt for local repro.

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Hello, using Alienware Area-51m R2, here my results. Thank you!
inxi.txt (4.7 KB) (448.2 KB)

(post deleted by author)

Sorry for the delay. I have attached the files. Unfortunately, even with 510.xx the issue is still present. On X11 at least xrandr can be used to spare your eyes. On wayland the display is stuck at full brightness.

acpidata.dat (877.3 KB)

And here’s the bug report.

nvidia-bug-report.log.gz (615.4 KB)

there are several things in this thread that are confusing the issue. To be clear the backlight does not work and has not worked since the post began for:
Laptops with Dedicated Nvidia Graphics Cards
The ones it has worked for are the hybrid which stopped working due to bios issues or driver issues from amd/intel. these operate the backlight with the systems backlight control, not nvidia. The other ‘it works’ posts come from using color correction to help… which is not backlight.
Nvidia’s dedicated graphics simply does not work and has not since the 460 series of drivers.
Feel free to message me, or just ignore. after over a year of trying to work through this I’ve about given up.


please stop pretending to be an authority on this matter. hybrid laptop backlight support is also broken.

the hybrid mode can be handled by amdgpu or nvidia driver. and adding amdgpu.backlight=0 to the command line is necessary to hand back control to nvidia driver.

thank you for looking into it. due to the abusive nature of one specific person on this thread who has continually sent direct personal attacks on every post i have made in the last two weeks I will no longer be monitoring. if you get a chance to review, please do and reach out directly if i can help in any way.

others are allowed to provide information or even correct assertions that you’ve made.

hybrid mode is broken as of any nvidia driver newer than 490.

just going to keep saying that hybrid mode is broken since v490 until the person flagging the post gets bored.