Hi everyone,
I discovered a work-around that actually seems to work. It definitely
keeps display at proper brightness when I log in. It was posted by
'Kubicle' on kubuntuforums.net.
I have an even more recent version of the kernel than this (-34), and
this still fixes it.
What you do is create the file containing the script listed in step 1.
** One thing I will add is to MAKE SURE the file name is '10-thinkpad-
backlight.fdi'. He did not have the .fdi on it.
Seems like a good work-around until the kernel really gets fixed.
It works on my T42, Kubuntu 10.04, KDE 4.5 (which, like KDE 4.4.x, still
had this display problem until I added this patch).
-Chris Murphy
* * * * * * * * * * * *
kubicle
Kubuntu Veteran
Offline
Posts: 2876
Thinking Inside the Box
Thinkpad backlight brightness bug in recent kernels [INCLUDES WORKAROUND]
« on: April 13, 2010, 01:45:45 am »
Bug Affects:
Thinkpad T41 (and possibly other models)
Kernels:
2.6.32-18 (Not bugged)
2.6.32-19 (Bugged)
2.6.32-20 (Bugged)
Symptoms:
- Display backlight brightness changes to the lowest value once kde starts to
load after logging in from kdm (once hal starts)
- Same happens when switching to X session from tty
- Cannot change display brightness with Powerdevil (kde's power manager), any
change dims display
- thinkpad extra buttons for changing backlight brightness (Fn+Home, Fn+End)
work normally.
Cause:
Difference in lshal output with nonbugged *-18 and bugged *-20 kernels
Quote
165c149
< laptop_panel.num_levels = 8 (0x8) (int)
---
> laptop_panel.num_levels = 1 (0x1) (int)
Workaround:
1. Create a custom hal policy file for forcing laptop_panel.num_levels value to
8:
file '/etc/hal/fdi/policy/10-thinkpad-backlight' contents:
Quote
<?xml version="1.0" encoding="ISO-8859-1"?> <!-- -*- SGML -*- -->
<deviceinfo version="0.2">
<device>
<match key="info.category" string="laptop_panel">
<match key="linux.sysfs_path" suffix="/backlight/thinkpad_screen">
<merge key="laptop_panel.num_levels" type="int">8</merge>
</match>
</match>
</device>
</deviceinfo>
2. Relog to restart hal
Remaining Issues:
Powerdevil display brightness slider still doesn't work as expected, but other
issues should be fixed.
This is just a workaround and not a definite fix (seems something was changed
between *-18 and *-19 kernel, and everything hasn't catched up with the change
yet)
--
Laptop display maximum dim at startup
https://bugs.launchpad.net/bugs/555709
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