thinkpad sl400 light control keys don't work

[julyfire]

My laptop is thinkpad sl400 ,the light control keys don't work in 9.04.Another problem is that the four keys on the left (a recover key and three sound control keys)don't work in any ubuntu,I hope you can give me a way to make them work.

[Courtney Wenman (0xception)]

I can confirm this problem... Also using a SL400 with 9.04 and noticed that the backlight buttons do not seem to function. When they are pressed (either fn+home or fn+end) the backlight is set to 0 or 1 and can only toggle between those two settings.

cat /sys/class/backlight/acpi_video0/brightness

The brightness settings do work at higher numbers

the fallowing will max it out.
echo 13 > /sys/class/backlight/acpi_video0/brightness

in 8.10 the brightness keys also were backwards, but you could always increase the backlight by lowering it, now you can't even do that, but the keys do seem to move it in the right direction (between 0 and 1)

[Simon Déziel (sdeziel)]

I have the same issue with Jaunty. I have also tested on Karmic and the bug is a bit different. First thing is that brightness can now go up to 15 instead of 13 in Jaunty (in /sys/class/backlight/acpi_video0/brightness). This matches what's reported in /proc/acpi :

cat /proc/acpi/video/VGA/LCDD/brightness
levels: 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 100
current: 100

On Jaunty the levels only go from 20 to 85. So that's a good improvement.

Second, I can now cycle through all the brightness settings but it's a bit random. When I press fn+home for the first time, brightness goes to 0. If I press it again it goes to 14. If I press fn+end and brightness is already at 15, it goes to 1. It goes back to 15 if I press it again.

Third, I can have every brightness level but I need to hold fn+home or fn+end for a certain amount of time and release it. It seems that the key press is sampled too fast.

[Simon Déziel (sdeziel)]

I've found a valid workaround for Karmic (does not work in Jaunty). You only have to do this :

echo 0 > /sys/module/video/parameters/brightness_switch_enabled

This comes from this link :
http://github.com/tetromino/lenovo-sl-laptop/blob/b19a08f81f693581013d7badfed6fd82e18a9a72/README

It fixes all my problems related to the brightness cycling.

[Simon Déziel (sdeziel)]

For Jaunty, my current workaround to get max brightness easily is to add a launcher in my menu bar.
The command is :

 sudo /usr/local/sbin/max-brightness

The content of this script is :

 #!/bin/sh
 FILE=/proc/acpi/video/VGA/LCDD/brightness
 MAX=`/usr/bin/awk '/^levels/ {print $NF}' $FILE`
 echo $MAX > $FILE

This file needs to be executable (chmod +x /usr/local/sbin/max-brightness). To make sure the user is not prompted for password every time it runs this script you can use "sudo visudo" to add the following lines :

 # Brightness fix
 NAME_OF_USER ALL=NOPASSWD: /usr/local/sbin/max-brightness

[penalvch (penalvch)]

julyfire, thank you for reporting this bug to Ubuntu. Jaunty reached EOL on October 23, 2010.
See this document for currently supported Ubuntu releases: https://wiki.ubuntu.com/Releases

Is this an issue in a supported release? If so, could you please execute the following command, as it will automatically gather debugging information, in a terminal:
apport-collect 348348

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]