Public bug reported:
This has been a common problem for various Thinkpad models for several
years. Mine currently is an X220 running Ubuntu 14.04.2 LTS (fully up-
to-date).
What happens is this.
1. The user presses the hotkey to increase/decrease the screen brightness.
2. The thinkpad_acpi module changes the brightness.
3. thinkpad_acpi reports the hotkey press.
4. The notification software also changes the brightness.
5. The osd notification shows the new brightness level.
Possible fixes.
1. sudo sh -c 'echo -n 0 >
/sys/module/video/parameters/brightness_switch_enabled'
2. Make the notification software not change the brightness on affected
Thinkpads OR at least provide a config option somewhere.
3. Stop thinkpad_acpi from reporting the keypress.
Disadvantages of the fixes
1. Brightness changing stops working on the text terminals and on the
lockscreen.
2. Changing brightness via slider in the System Settings app will possibly stop
working.
3. No OSD for brightness changes. And anyway setting the hotkey_mask currently
has no effect on the brightness hotkeys on my X220 running Trusty though it
does effect other hotkeys.
The ideal fix is obviously number 2, but I could live with any of the
others.
** Affects: indicator-power (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1452245
Title:
Brightness via hotkey skips steps
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