Backlight brightness control doesn't work
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux (Ubuntu) |
Confirmed
|
Medium
|
Unassigned |
Bug Description
Hello, during a kernel update from 3.11.0-4 up to 3.11.0-9 i've found out that my brightness controll of my Notebook (Lenovo Thinkpad T430-D17 (nvidia-graphic card, optimus disabled, driver version: 325.15) does not work). Therefore, i have tried several kernel from kernel.org where all Kernel provides the backlight control. To get comparable values, i have tried the kernel version
ubuntu-kernel: Ubuntu 3.12.0-0.2-generic and 3.12.0-rc6
By using the the ubuntu kernel, i wasn't able to control the backlight brightness but by using the kernel profided by kernel.org works. Therefore, i began to search the patch lists of ubuntu and find this patch: http://
I have reverted this patch and the brightness control of my notebook works fine.
If anybody wants to execute the ubuntu-bug program, you should note, that i'm not using ubuntu, i'm only using the ubuntu kernel and the ubuntu-bug program is not in my repositories. Therefore, i supply the lspci-vnvn report. If any other logs or reports are missing please feel free to ask me.
Changed in linux (Ubuntu): | |
importance: | Undecided → Medium |
tags: | added: saucy |
tags: |
added: needs-kernel-logs needs-upstream-testing regression-potential removed: acpi backlight lenovo t430 thinkpad |
Björn: We also have reports that this patch fixes the backlight on the T430 (bug #1183856). Possibly Lenovo is making machines that look the same to the kernel but behave differently.
Please also provide the following information.
Grab a copy of your acpi tables by running "acpidump > acpi-tables.txt" and attach acpi-tables.txt here.
Also grab a copy of your dmi information by running "dmidecode > dmi.txt" and attach dmi.txt here.
Then, please do the following twice, once with an Ubuntu kernel where your backlight works and once with one where it doesn't.
1. Capture dmesg output and attach it here.
2. Provide the output from "ls /sys/class/ backlight" .
3. For each of the directories in /sys/class/ backlight, run "cat max_brightness" to find the maximum brightness value supported. Then try writing a few values between 1 and max_brightness to the brightness file, e.g. "echo 10 | sudo tee brightness". Working backlights should change brightness each time you write a new value to brightness. Let me know which backlights work and which do not.