[Powerdevil] [Bug 351209] New: Brightness setting for "On Battery" works only for a very low brightness level

[a.pronobis at gmail.com]

https://bugs.kde.org/show_bug.cgi?id=351209

            Bug ID: 351209
           Summary: Brightness setting for "On Battery" works only for a
                    very low brightness level
           Product: Powerdevil
           Version: 5.3.90
          Platform: Ubuntu Packages
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: general
          Assignee: plasma-devel at kde.org
          Reporter: a.pronobis at gmail.com

After enabling "Screen brightness" control in the "On battery" profile, the
brightness when running on battery does not change automatically unless the
"Level" is set to a very low value (sth around 10%). For such low value,
unplugging AC will indeed affect brightness. If the level is set to any higher
value, e.g. 50%, unplugging AC will not affect brightness at all.  Brightness
settings for "On AC Power" profile work without problems for any brightness
level.

This behavior can be observed using udeavadm monitor, which for the low level
value shows for AC unplug event:

KERNEL[2565.602739] change  
/devices/pci0000:00/0000:00:02.0/backlight/acpi_video0 (backlight)
UDEV  [2565.604719] change  
/devices/pci0000:00/0000:00:02.0/backlight/acpi_video0 (backlight)

If higher level is set, udev only reports setting brightness when plugging IN
the AC, but not when unplugging.

Keyboard backlight also does not seem to work for the On Battery profile, while
it does work for "On AC power".

Reproducible: Always

Steps to Reproduce:
1. Enable Screen brightness for "On Battery" profile and set the level to 50%
2. Unplug AC
3. Observe that the brightness did not change
4. Plug in AC
5. Set brightness level to around 5%
6. Unplug AC
7. Observe that brightness has been changed

Actual Results:  
As in the steps, brightness is not affected for certain level settings.

Expected Results:  
Brightness should be adjusted no matter what level is set.

Running Ubuntu 15.10 with KDE 5.3.95.

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