DT support for Low threshold brightness in backlight.

From: Philip, Avinash
Date: Wed Jul 18 2012 - 11:00:49 EST


In pwm-backlight driver low threshold brightness support in DT is not
present. Do you have any plans in such direction?

I am planning to add support for the same but want to avoid duplication
of work.

Below scenario describes need for it:
On some boards panel backlight is OFF at low end of brightness scale.
So with Low threshold brightness we can have linear scale in brightness
(Though the actual brightness scale is changes to Low threshold
brightness value instead of 0).

Example with Low threshold brightness
pwms = <&pwm 0 50000>;
brightness-levels = <0 2 4 8 16 32 64 128 255>;
default-brightness-level = <6>;
brightness_threshold_level = <50>;

It can also be achieved without Low threshold brightness as below

pwms = <&pwm 0 50000>;
brightness-levels = <0 51 53 56 62 75 101 152 255>;
default-brightness-level = <6>;

But brightness-levels won't be uniformly divided.

So it is good to have low threshold DT support for backlight.

Avinash Philip

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