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  1. Bug #1098216
  2. Comment #0

Comment 0 for bug 1098216

Revision history for this message
Stéphane Graber (stgraber) wrote : Regression in brightness control on Lenovo Thinkpad x230

Something changed between the 3.5 and the 3.7 kernel, leading to broken brightness control on my Thinkpad x230.

Here are some test results:
== 3.5.0-21-generic ==
=== Post-boot values ===
/sys/class/backlight:
  - intel-backlight
    + actual_brightness => 4438
    + bl_power => 0
    + brightness => 4438
    + max_brightness => 4438
  - acpi_video0
    + actual_brightness => 15
    + bl_power => 0
    + brightness => 15
    + max_brightness => 15

=== Tests ===
echo 0 > acpi_video0/brightness => works
echo 0 > intel_backlight/brightness => works

== 3.8.0-0-generic ==
=== Post-boot values ===
/sys/class/backlight:
  - intel-backlight
    + actual_brightness => 4438
    + bl_power => 0
    + brightness => 4438
    + max_brightness => 4438
  - acpi_video0
    + actual_brightness => 100
    + bl_power => 0
    + brightness => 100
    + max_brightness => 100

=== Tests ===
echo 0 > acpi_video0/brightness => doesn't do anything
echo 0 > intel_backlight/brightness => works