sets wrong brightness value with xrandr

[Kai Jauch]

Binary package hint: gnome-power-manager

My laptop display backlight has 16 brightness values (0-15). If gnome-power-manager is not running and I set it all the way down to 0 (via fn-brightness-down) and watch /sys/class/backlight/acpi_video0/actual_brightness as I incrementally turn it up to full brightness again, I see the values 0, 1, 2, ... 15 as one would expect.
If gnome-power-manager is running, I see the values 0, 2, 4, 6, 8, ..., 14, 15, i.e. jumping two levels up each time I increase the brightness one step. The backlight however really only increases the level by one each time I press fn-brightness-up, so when actual_brightness reaches 15 the actual brightness I see on my display is around half of the full backlight level.

This causes the brightness notifications from notify-osd to report bogus values (thinking I already reached maximum when I'm just on half brightness etc.)

This behaviour started very recently, probably when the xrandr-backlight KMS capability was enabled, it was working fine before.
I'm not sure whether this is actually the fault of xserver-xorg-video-intel or the kernel, but as I see those bogus values only when gnome-power-manager is running I decided to file it against that. I have an Intel GM45 on a Dell Latitude E6400.

Attaching the output of gnome-power-manager --verbose when incrementally setting the brightness from zero to full.

ProblemType: Bug
Architecture: amd64
Date: Sat Oct 17 09:41:01 2009
DistroRelease: Ubuntu 9.10
Package: gnome-power-manager 2.28.0-0ubuntu7
ProcEnviron:
 PATH=(custom, user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-14.48-generic
SourcePackage: gnome-power-manager
Uname: Linux 2.6.31-14-generic x86_64
XsessionErrors:
 (gnome-settings-daemon:2554): GLib-CRITICAL **: g_propagate_error: assertion `src != NULL' failed
 (gnome-settings-daemon:2554): GLib-CRITICAL **: g_propagate_error: assertion `src != NULL' failed
 (polkit-gnome-authentication-agent-1:2667): GLib-CRITICAL **: g_once_init_leave: assertion `initialization_value != 0' failed
 (nautilus:2646): Eel-CRITICAL **: eel_preferences_get_boolean: assertion `preferences_is_initialized ()' failed
 (Do:2666): Wnck-CRITICAL **: wnck_set_client_type got called multiple times.

[Kai Jauch (kaijauch)]

The behavior has changed: Pressing fn-brightness-up/down while gnome-power-manager is running still causes actual_brightness to jump up/down two levels on each keypress, but it now represents the correct brightness (i.e. my display backlight really increases or decreases its brightness by two levels).
I believe that the keypress is both handled by my laptop directly and by gnome-power-manager. BIOS (or hardware directly, however this is actually implemented) reacts to fn-brightness-up by increasing the brightness one level. g-p-m also reacts to the keypress by increasing the brightness by one level. This causes the backlight to actually increase its brightness twice on a single keypress.

lshal reports for my backlight:

udi = '/org/freedesktop/Hal/devices/computer_backlight'
  info.addons = {'hald-addon-generic-backlight'} (string list)
  info.capabilities = {'laptop_panel'} (string list)
  info.category = 'laptop_panel' (string)
  info.interfaces = {'org.freedesktop.Hal.Device.LaptopPanel'} (string list)
  info.parent = '/org/freedesktop/Hal/devices/computer' (string)
  info.product = 'Generic Backlight Device' (string)
  info.subsystem = 'backlight' (string)
  info.udi = '/org/freedesktop/Hal/devices/computer_backlight' (string)
  laptop_panel.access_method = 'general' (string)
  laptop_panel.brightness_in_hardware = false (bool)
  laptop_panel.num_levels = 16 (0x10) (int)
  linux.hotplug_type = 2 (0x2) (int)
  linux.subsystem = 'backlight' (string)
  linux.sysfs_path = '/sys/devices/virtual/backlight/acpi_video0' (string)

laptop_panel.brightness_in_hardware being set to false is wrong, my laptop supports that.

[Kai Jauch (kaijauch)]

Architecture: amd64
Dependencies:

DistroRelease: Ubuntu 9.10
Package: hal-info 20090716-0ubuntu1
PackageArchitecture: all
ProcEnviron:
 SHELL=/bin/bash
 PATH=(custom, user)
 LANG=de_DE.UTF-8
ProcVersionSignature: Ubuntu 2.6.31-14.48-generic
Uname: Linux 2.6.31-14-generic x86_64
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare

[Maarten Jongepier (jongep86)]

Maybe 'duplicate' of this bug https://bugs.launchpad.net/ubuntu/+source/gnome-power-manager/+bug/415023

That's only the MSI wind but it looks very similar; xrandr and hardware both at the same time setting the brightness.