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
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: backlight:
== 3.5.0-21-generic ==
=== Post-boot values ===
/sys/class/
- 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 === brightness => works /brightness => works
echo 0 > acpi_video0/
echo 0 > intel_backlight
== 3.8.0-0-generic == backlight:
=== Post-boot values ===
/sys/class/
- 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 === brightness => doesn't do anything /brightness => works
echo 0 > acpi_video0/
echo 0 > intel_backlight