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[Seth Forshee <seth.forshee+lp@xxxxxxxxxxxxx>]

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.

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https://bugs.launchpad.net/bugs/1243267

Title:
  Backlight brightness control doesn't work

Status in “linux” package in Ubuntu:
  Incomplete

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://kernel.ubuntu.com/git?p=ubuntu/ubuntu-trusty.git;a=blobdiff;f=drivers/acpi/blacklist.c;h=f49ffaedaefdaa28d533d339a3f5cda073687ed7;hp=9515f18898b2b578053c58309185daa7934cfdda;hb=02cb06962306d96f59bc97ec8289c14b73bafb4e;hpb=2eb9acd1a1deb3f4d6428d022fc43541c9e70069.
  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.

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