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

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Message-ID: <c13b67ec-c030-302a-6315-fad18323923a@linaro.org>
Date:   Wed, 30 Nov 2022 12:59:51 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Chuanhong Guo <gch981213@...il.com>
Cc:     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

On 30/11/2022 10:25, Chuanhong Guo wrote:
> Hi!
> 
> On Wed, Nov 30, 2022 at 5:08 PM Krzysztof Kozlowski
> <krzysztof.kozlowski@...aro.org> wrote:
>> And that's exactly what I said - the compatibles should not include bus
>> information. The bus information comes from... the bus!
> 
> Oh. I thought there will be a conflict if there is a SPI driver and
> , say, an I2C driver with the same compatible string.

We already have such. For example: adi,adxl312

> 
>> [...]
>>>>
>>>> Why unit address is optional?
>>>
>>> It isn't. I copy-pasted it from led-class-multicolor.yaml and
>>> didn't check the exact regex.
>>> I'll fix it in the next version.
>>
>> Make it required and matching your case.
> 
> Got it.
> 
>> [...]
>>>>> +      default-intensity:
>>>>> +        description: |
>>>>> +          An array of 3 integer specifying the default intensity of each color
>>>>> +          components in this LED. <255 255 255> if unspecified.
>>>>> +        $ref: /schemas/types.yaml#/definitions/uint32-array
>>>>> +        minItems: 3
>> [...]
>> So this is brightness of each color...
> 
> I don't think so.
> See the kernel doc for multicolor LED:
> https://docs.kernel.org/leds/leds-class-multicolor.html
> This property sets the sysfs file multi_intensity while the
> actual LED brightness is controlled with another sysfs
> file called 'brightness'.
> Setting multi_intensity alone doesn't change the LED
> brightness at all.

If you had brightness, that would be correct. But you do not have
brightness, right? Therefore the final brightness is always:

subled[i].brightness = 255 * subled[i].intensity / max_brightness (also
255);

Or your bindings are incomplete...

Best regards,
Krzysztof