linux-kernel - Re: [PATCH 3/3] arm64: dts: qcom: sm7225-fairphone-fp4: configure flash LED

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Date:   Thu, 23 Mar 2023 20:54:24 +0100
From:   Pavel Machek <pavel@....cz>
To:     Fenglin Wu <quic_fenglinw@...cinc.com>
Cc:     Luca Weiss <luca.weiss@...rphone.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-leds@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] arm64: dts: qcom: sm7225-fairphone-fp4: configure
 flash LED

Hi!


> > > I'm pretty sure the flash is not yellow.
> > 
> > The marketing term is Dual LED flash or Dual-tone flash, one LED is a
> > blue-ish white and one is a yellow-ish white, but from what I can tell,
> > in the original code it's always referred to as white and yellow so I
> > also followed that here.
> > 
> > Also the LEDs are right next to each other so in practise for torch just
> > both go on, and for camera flash I cannot really tell you but I guess
> > it's doing something there with the camera tuning.
> > 
> > See also this picture:
> > https://shop.fairphone.com/media/catalog/product/cache/b752d78484639b19641a8560800d919d/p/_/p_5b_main_camera_back.jpg
> > 
> Hi Pavel,
> 
> Luca is right. It is normally called dual CCT (Correlated Color Temperature)
> flash LED. It has 2 LEDs, one is with higher CCT (~6000K) so it looks like a
> white LED, another is with lower CCT (~2000K) and it looks like a yellow
> LED. I am not an expert of this but my understanding is the camera tuning
> process normally adjusts the brightness of the two LEDs and enables them to
> get different CCT for different snapshots.

I believe this is normally called "warm white" and "cool white", no?
Yellow would be monochromatic light at cca 575nm, see
https://en.wikipedia.org/wiki/Shades_of_yellow .

If we need to add some defines for that, lets do that.

BR,
									Pavel
-- 
People of Russia, stop Putin before his war on Ukraine escalates.

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