[Bug 72120] Screen brightness not altered when AC adapter is unplugged

[Robert Knight]

Public bug reported:

Binary package hint: kde-guidance-powermanager

I have a SONY VAIO Z1RSP laptop.

When unplugging the power adapter the screen brightness is not adjust in
accordance with the settings in the new "Power Management" dialog.

The laptop keys to adjust the screen brightness and gnome's Power
Manager utility both work, so I am assuming this is not a problem with
the kernel.  The /etc/acpi/sonybright.sh script also works correctly.

I didn't have any luck trying to set the value using HAL/DBus and the
commandline dbus-send tool though:

robert at robert-laptop:~$ dbus-send --print-reply --system --dest=org.freedesktop.Hal /org/freedesktop/Hal/devices/acpi_brightness org.freedesktop.Hal.Device.LaptopPanel.SetBrightness int32:2
method return sender=:1.0 -> dest=:1.101
   uint32 2


I believe another VAIO user reported a similar problem in the "Kubuntu Power Management Feedback" wiki page.

Below is output from hal-device which I hope is relevant:

----------------
9: udi = '/org/freedesktop/Hal/devices/acpi_brightness'
  info.udi = '/org/freedesktop/Hal/devices/acpi_brightness'  (string)
  org.freedesktop.Hal.Device.LaptopPanel.method_execpaths = { 'hal-system-lcd-set-brightness', 'hal-system-lcd-get-brightness' } (string list)
  org.freedesktop.Hal.Device.LaptopPanel.method_signatures = { 'i', '' } (string list)
  org.freedesktop.Hal.Device.LaptopPanel.method_names = { 'SetBrightness', 'GetBrightness' } (string list)
  info.interfaces = { 'org.freedesktop.Hal.Device.LaptopPanel' } (string list)
  linux.hotplug_type = 4  (0x4)  (int)
  info.capabilities = { 'laptop_panel' } (string list)
  laptop_panel.num_levels = 8  (0x8)  (int)
  laptop_panel.access_method = 'sony'  (string)
  info.product = 'Sony LCD Panel'  (string)
  info.category = 'laptop_panel'  (string)
  info.parent = '/org/freedesktop/Hal/devices/computer'  (string)
  linux.acpi_type = 8  (0x8)  (int)
  linux.acpi_path = '/proc/acpi/sony/brightness'  (string)
------------------------

** Affects: kde-guidance (Ubuntu)
     Importance: Undecided
         Status: Unconfirmed

-- 
Screen brightness not altered when AC adapter is unplugged
https://launchpad.net/bugs/72120