* DT support for Low threshold brightness in backlight.
@ 2012-07-18 14:59 Philip, Avinash
2012-07-23 8:32 ` Thierry Reding
0 siblings, 1 reply; 2+ messages in thread
From: Philip, Avinash @ 2012-07-18 14:59 UTC (permalink / raw)
To: rpurdie, Thierry Reding; +Cc: linux-kernel, Nori, Sekhar, Hebbar, Gururaja
Hi,
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.
Thanks
Avinash Philip
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: DT support for Low threshold brightness in backlight.
2012-07-18 14:59 DT support for Low threshold brightness in backlight Philip, Avinash
@ 2012-07-23 8:32 ` Thierry Reding
0 siblings, 0 replies; 2+ messages in thread
From: Thierry Reding @ 2012-07-23 8:32 UTC (permalink / raw)
To: Philip, Avinash; +Cc: rpurdie, linux-kernel, Nori, Sekhar, Hebbar, Gururaja
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On Wed, Jul 18, 2012 at 02:59:32PM +0000, Philip, Avinash wrote:
> Hi,
>
> 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.
>
> Thanks
> Avinash Philip
I have no plans to add it myself, but feel free to send a patch. There
is a corresponding field in the platform data already, so adding DT
support is probably a good idea.
Thierry
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