[lm-sensors] [PATCH] hwmon: applesmc: restore keyboard backlight on resume

Henrik Rydberg rydberg at euromail.se
Mon Aug 24 23:49:20 CEST 2009

Andrew Morton wrote:
> On Sat, 22 Aug 2009 23:33:52 +0200
> "Henrik Rydberg" <rydberg at euromail.se> wrote:
>> On resume from suspend, the driver currently resets the logical
>> state as if it was brought up from halt. This patch uses the
>> dev_pm_ops.resume method to synchronize the hardware with the
>> memorized logical state, bringing back the backlight to the level
>> prior to suspend.
> What are the runtime effects of this change?

The patch has zero impact on a running system, only suspend/resume
behavior is affected.

Precondition: Suspend computer with keyboard backlight brightness
greater than zero.

Before patch: On resume, the backlight stays off.

After patch: On resume, the backlight is set to the brightness prior to

There is one side-effect of the patch: the accelerometer no longer
re-calibrates on resume, but keeps the calibration from before suspend.
I consider this a good change, but it is after all a change.


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