Cannot control brightness / backlight of Dell notebook

I think it has something to do with hal, as even kpowersave can't change the brightness.

Using the FN-keys to change the brightness works, but being able to change it by software can help saving power when running on batteries.

Thank you for taking the time to report this bug and helping to make Ubuntu better. It would be helpful to know which version of Ubuntu you noticed this issue? Additionally, the specific package versions of hal and kde-guidance that you have installed, you can check with 'apt-cache policy hal', would be really helpful too. Thanks in advance.

Sorry for not providing package information earlier.

Version of Ubuntu: latest hardy, updated daily (kubuntu edition)

hal:
  Installed: 0.5.10-5ubuntu8
  Candidate: 0.5.10-5ubuntu8

kde-guidance:
  Installed: 0.8.0svn20080103-0ubuntu1
  Candidate: 0.8.0svn20080103-0ubuntu1

kpowersave:
  Installed: 0.7.3-1ubuntu1
  Candidate: 0.7.3-1ubuntu1

linux-image-generic:
  Installed: 2.6.24.11.11
  Candidate: 2.6.24.11.11

Added package information

modinfo dcdbas
filename: /lib/modules/2.6.24-11-generic/kernel/drivers/firmware/dcdbas.ko
alias: dmi:*:[bs]vnD[Ee][Ll][Ll]*:*
license: GPL
author: Dell Inc.
version: 5.6.0-3.2
description: Dell Systems Management Base Driver (version 5.6.0-3.2)
srcversion: 0A5B6E3056A439D49C7FD88
depends:
vermagic: 2.6.24-11-generic SMP mod_unload

This module is loaded via /etc/modules at boot.

In some discussions I read that it should be possible to set the brightness via /proc/acpi/video/VID/LCD/brightness, but this seems not to be supported:

cat /proc/acpi/video/VID/LCD/brightness
<not supported>

Again, I can change the brightness via the FN-keys - only changing by software doesn't work - and any program trying to change the brightness hangs with an error message:

Warning: in getBrightness(): org.freedesktop.DBus.Error.NoReply: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.

This bug is probably related to Bug #191725 - I'm testing the new hal-package right now and will provide more info later on.

The patch provided in Bug #191725 doesn't solve this problem.

The patch I'm applying for Bug #183656 should at least solve the powermanager crashes part of this. Beyond that, I don't think powermanager can do anything about this if dbus doesn't answer.

This bug was fixed in the package kde-guidance - 0.8.0svn20080103-0ubuntu2~ppa3

---------------
kde-guidance (0.8.0svn20080103-0ubuntu2~ppa3) hardy; urgency=low

  * Add kubuntu_10_displayconfig_tryagain.patch so that if displayconfig
    thinks a proprietary driver is installed, but it can't find it, it
    will try to find a non-proprietary driver instead of crashing (LP: #198269)
  * Add kubuntu_11_wineconfg_amd64.patch so that wineconfig looks in the right
    dir for wine on AMD64 (LP: #151982) - Patch should be removed for the next
    svn snapshot or release as a fix has been committed upstream already
  * Add kubuntu_12_powermanager_survive_no_brightness.patch so that if the old
    brightness cannot be gotten from DBUS, powermanager won't crash
    (LP: #183656) and (LP: #198071)
  * Add kubuntu13_displayconfig_add_new_monitors.patch to support additional
    ViewSonic VA702 variants (LP: #192899)

 -- Scott Kitterman <email address hidden> Tue, 04 Mar 2008 11:14:41 -0500

Fix is not actually released yet. Please test the updated kde-guidance-powermanager in my PPA:

https://launchpad.net/~kitterman/+archive

If I get confirmation the fix works, I'll include it in the next upload.

Bug #183656 is solved by this fix (0.8.0svn20080103-0ubuntu2~ppa3), the problem reported here is still present - the brightness cannot be set on the Dell Latitude D620.

As kde-guidance and kpowersave are both not able to set the brightness, and I think they are just sending DBUS-messages, the probably is cause by either HAL or the kernel module itself.

Is there any way to test the kernel module directly?

This bug was fixed in the package kde-guidance - 0.8.0svn20080103-0ubuntu3

---------------
kde-guidance (0.8.0svn20080103-0ubuntu3) hardy; urgency=low

  * Add Add kubuntu_09_mountconfig_no_extensions.patch to remove uneeded call
    to pykdeextensions in mountconfig so that pyqt3 no longer needs to be
    patched to provide -dev files in the regular package (LP: #197867)
  * Add kubuntu_10_displayconfig_tryagain.patch so that if displayconfig
    thinks a proprietary driver is installed, but it can't find it, it
    will try to find a non-proprietary driver instead of crashing (LP: #198269)
  * Add kubuntu_11_wineconfg_amd64.patch so that wineconfig looks in the right
    dir for wine on AMD64 (LP: #151982) - Patch should be removed for the next
    svn snapshot or release as a fix has been committed upstream already
  * Add kubuntu_12_powermanager_survive_no_brightness.patch so that if the old
    brightness cannot be gotten from DBUS, powermanager won't crash
    (LP: #183656) and (LP: #198071)
  * Add kununtu_13_displayconfig_add_new_monitors.patch to update MonitorsDB
    with a upstream snapshot of MonitorsDB from hwdata (LP: #192899)

 -- Scott Kitterman <email address hidden> Sun, 09 Mar 2008 19:53:42 -0400

Problem was not caused by kernel module.

This problem was not caused by kpowersave.

There is an hal related issue regarding this problem, therefore I will open a new bug report for this later.

The problem was in relation to libsmbios. The BIOS of my laptop computer is secured with a password, therefore libsmbios and hal couldn't set the brightness. Removing the password solves this problem.

Link to upstream bug report (just for reference): http://bugs.freedesktop.org/show_bug.cgi?id=7221