linux-kernel - Re: [PATCH 2/3] dt-bindings: leds: add dt schema for worldsemi,ws2812b-spi

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Date:   Wed, 30 Nov 2022 16:38:39 +0800
From:   Chuanhong Guo <gch981213@...il.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Sebastian Reichel <sre@...nel.org>, linux-leds@...r.kernel.org,
        Pavel Machek <pavel@....cz>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Stanislav Jakubek <stano.jakubek@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Johan Hovold <johan+linaro@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Sven Schwermer <sven.schwermer@...ruptive-technologies.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] dt-bindings: leds: add dt schema for worldsemi,ws2812b-spi

Hi!

On Wed, Nov 30, 2022 at 4:33 PM Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
> >> What controls the intensity? Don't you have PWM there?
> >
> > WS2812 is a RGB led, which contains a small Microcontroller. The µC
> > takes 24 byte intensity data from a serial input and then passes on
> > any following bits to the next LED. SPI clk and chip-select are
> > ignored (chip-select support can be trivially added though).
> >
> > You can find them everywhere nowadays, since they are quite cheap
> > (a few cents per LED) and need only one MOSI pin to control hundreds
> > of LEDs.
>
> OK. This should be anyway existing property, so default-brightness.

default-intensity is a different property. Intensity controls only the
color for a multicolor led. The final brightness is calculated with
this intensity value with the single brightness value of the current
LED. (See my previous mail.)

-- 
Regards,
Chuanhong Guo