[Ubuntu Wiki] Update of "Kernel/Debugging/Backlight" by penalvch

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Mon Jun 25 10:33:56 UTC 2012


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The "Kernel/Debugging/Backlight" page has been changed by penalvch:
http://wiki.ubuntu.com/Kernel/Debugging/Backlight?action=diff&rev1=9&rev2=10

Comment:
Added polished Report Minimum Requirements section as per https://lists.launchpad.net/ubuntu-bugcontrol/msg03742.html

   * Backlight control does not work and there are no entries in {{{/sys/class/backlight}}}.
    * Neither the ACPI backlight driver nor any vendor specific driver were able to find a valid interface. Either requires a new vendor driver (which is unlikely) or the ACPI BIOS is broken (see below). Updates to the ACPI BIOS are rare as well but in some cases it is possible to work with upstream to extend the Linux side to handle some of that brokenness.
  
- = Filing Bugs =
+ = Reporting Backlight Bugs =
  
+  * Please do not report a backlight bug without first reading this wiki article and performing all the relevant actions mentioned here. Failure to do so will delay your bug getting addressed as quickly as possible.
- When filing bugs about backlight control, try to classify the issue into the classes above. Also describe whether there was a previous kernel that worked, or whether this was never the case. Also be very specific in the bug title about the laptop vendor and model. Backlight control is very specific to hardware and a bug titled "''backlight control does not work''" just causes other people to use that bug even if they have a completely different laptop. It is much simpler to look into issues separately than to mix things.
+  * When filing bugs about backlight control, please classify the issue into one of the classes above. Also describe whether there was a previous kernel that worked, or whether this was never the case. Also be very specific in the bug title about the laptop vendor and model. Backlight control is very specific to hardware and a bug titled "''backlight control does not work''" just causes other people to use that bug even if they have a completely different laptop. It is much simpler to look into issues separately than to mix things.
- 
- Also, depending on the class of issues, provide additional information about the kernel interface. Does it exist, do any values change when writing into the control files? Is there any effect?
+  * Also, depending on the class of issues, provide additional information about the kernel interface. Does it exist, do any values change when writing into the control files? Is there any effect?
- 
- If the kernel interface does not work, add the dump of the ACPI BIOS as described below.
+  * If the kernel interface does not work, add the dump of the ACPI BIOS as described below.
+ 
+ == Report Minimum Requirements ==
+ 
+  * Please file backlight bugs by executing at the Terminal: <<BR>> {{{ubuntu-bug linux}}} <<BR>> <<BR>> If it turns out to be a non-linux package issue, it can be changed to the appropriate package.
+  * Install the prerequisites by executing at the Terminal: <<BR>> {{{sudo apt-get install -y acpidump fwts dmidecode}}}
+  * Execute each of the following via a terminal, and post the results to your report: <<BR>> {{{grep -r . /proc/acpi/video}}} <<BR>> {{{ls /sys/class/backlight}}} <<BR>> {{{sudo acpidump -o acpidump.txt}}} <<BR>> {{{acpixtract acpidump.txt}}} <<BR>> {{{iasl -d DSDT.dat}}} <<BR>> {{{sudo fwts > fwts}}} <<BR>> {{{sudo fwts method > fwts method}}} <<BR>> {{{dmesg | grep 'ACPI: Video'}}} <<BR>> {{{dmidecode > dmidecode.log}}} <<BR>> {{{cat /proc/version}}}
+  * Add kernel parameter atkbd.softraw=0 to /boot/grub/menu.lst . Then, switch to any console, e.g. Ctrl+Alt+F1, login by root account and execute: {{{showkey -s}}} <<BR>> <<BR>> Then, press Fn+Left and Fn+Right key to check the code that shows up on screen. Post the results to the report. For example: <<BR>> <<BR>> Fn+Left: <<BR>> 0xe0 0x4c 0xe0 0xcc <<BR>> <<BR>> Fn+Right: <<BR>> 0xe0 0x54 0xe0 0xd4
+ 
+ === Thinkpads ===
+ 
+  * Add kernel parameters thinkpad-acpi.brightness_enable=1 acpi_backlight=vendor to /boot/grub/menu.lst . Execute: <<BR>> {{{sudo update grub}}} <<BR>> <<BR>> Restart, and comment on if brightness may be changed via hotkeys and/or brightness applet.
+  ** As well, execute the following and post results to your report: <<BR>> {{{lsmod | grep thinkpad_acpi}}}
+ 
+ === Intel ===
+ 
+  * If using an intel board, add the kernel parameter acpi_backlight=vendor /boot/grub/menu.lst . Execute: <<BR>> {{{sudo update grub}}} <<BR>> <<BR>> Restart, and comment on if brightness may be changed via hotkeys and/or brightness applet. Then execute the following and post results to your report: <<BR>> {{{ls -la /sys/class/backlight/intel_backlight/}}}
+ 
+  * Comment on how the brightness changes if one executes: <<BR>> {{{sudo su}}} <<BR>> {{{sudo echo 8 > /sys/class/backlight/intel_backlight/brightness}}}
  
  = Diagnostic Techniques =
  



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