linux-kernel - Re: [RFC PATCH 2/5] dt: bindings: Add multicolor class dt bindings documention

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Date:   Tue, 2 Apr 2019 12:06:52 -0500
From:   Dan Murphy <dmurphy@...com>
To:     Marek Behun <marek.behun@....cz>
CC:     Pavel Machek <pavel@....cz>, <robh+dt@...nel.org>,
        <jacek.anaszewski@...il.com>, <linux-kernel@...r.kernel.org>,
        <linux-leds@...r.kernel.org>,
        Vesa Jääskeläinen <dachaac@...il.com>
Subject: Re: [RFC PATCH 2/5] dt: bindings: Add multicolor class dt bindings
 documention

Marek

On 4/2/19 11:17 AM, Marek Behun wrote:
> On Tue, 2 Apr 2019 06:40:53 -0500
> Dan Murphy <dmurphy@...com> wrote:
> 
>> I have had off line conversations with Jacek about this brightness model node.
>>
>> Your concern was actually one of my concerns as well.  Not only millions of entries but also having a huge
>> DT binary.
>>
>> We wanted to RFC this to get feedback.  And this is why I have not added any support for this in the framework code.
>>
>> Dan
>>
> 
> What if we just stuck to color spaces and defined channel curves in the
> device tree?
> 

Vesa did a good summary of the current MC framework implementations that are being proposed
The thread also documents Pavel's requirements

https://lore.kernel.org/patchwork/patch/1037147/

And here is the series with a single brightness file and passing in multiple integers.
I did not document this code as I was pretty certain it was not the way to go.

https://patches.linaro.org/project/linux-leds/list/?series=18022

Dan

> The curve could then be defined via an array of integer pairs, which
> would be interpreted as points via which the curve passes and the curve
> would be approximated by linear segemts...
> 
>   led@0 {
>     colorspace = <COLOR_SPACE_ID_RGB>;
>     red-curve = <0 0>, <255 255>;
>     green-curve = <0 0>, <255 128>;
>     blue-curve = <0 0>, <255 128>;
>   };
> 


-- 
------------------
Dan Murphy