linux-kernel - Re: [PATCH v4 2/3] dt-bindings: leds: add worldsemi,ws2812b

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Message-ID: <9d2c05f6-af5a-2d79-02ea-85c49e244957@linaro.org>
Date:   Sat, 24 Dec 2022 13:53:56 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Pavel Machek <pavel@....cz>
Cc:     Chuanhong Guo <gch981213@...il.com>, linux-leds@...r.kernel.org,
        Lee Jones <lee@...nel.org>, 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 v4 2/3] dt-bindings: leds: add worldsemi,ws2812b

On 23/12/2022 18:19, Pavel Machek wrote:
> Hi!
> 
>>> Add dt binding schema for WorldSemi WS2812B driven using SPI
>>> bus.
>>>
>>> Signed-off-by: Chuanhong Guo <gch981213@...il.com>
>>> ---
>>> Changes since v1:
>>> remove linux driver reference from description
>>> remove some obvious descriptions
>>> fix unit address regex in multi-led property
>>> drop various minItems
>>> add maxItems = 1 to reg
>>> fix node names and property orders in binding example
>>> drop -spi from compatible string
>>> add default-brightness
>>>
>>> Change since v2:
>>> drop "this patch" from commit message
>>> rename leds to led-controller
>>> drop default-brightness and default-intensity
>>>
>>> Change since v3:
>>> reword commit title
>>>
>>>  .../bindings/leds/worldsemi,ws2812b.yaml      | 116 ++++++++++++++++++
>>>  1 file changed, 116 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/leds/worldsemi,ws2812b.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/leds/worldsemi,ws2812b.yaml b/Documentation/devicetree/bindings/leds/worldsemi,ws2812b.yaml
>>> new file mode 100644
>>> index 000000000000..548c05ac3d31
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/leds/worldsemi,ws2812b.yaml
>>> @@ -0,0 +1,116 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/leds/worldsemi,ws2812b.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: WS2812B LEDs driven using SPI
>>> +
>>> +maintainers:
>>> +  - Chuanhong Guo <gch981213@...il.com>
>>> +
>>> +description: |
>>> +  WorldSemi WS2812B is a individually addressable LED chip that can be chained
>>> +  together and controlled individually using a single wire.
>>> +  This binding describes a chain of WS2812B LEDs connected to the SPI MOSI pin.
>>> +  Typical setups includes connecting the data pin of the LED chain to MOSI as
>>> +  the only device or using CS and MOSI with a tri-state voltage-level shifter
>>> +  for the data pin.
>>> +  The SPI frequency needs to be 2.105MHz~2.85MHz for the timing to be correct
>>> +  and the controller needs to send all the bytes continuously.
>>> +
>>> +allOf:
>>> +  - $ref: /schemas/spi/spi-peripheral-props.yaml#
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: worldsemi,ws2812b
>>> +
>>> +  reg:
>>> +    maxItems: 1
>>> +
>>> +  spi-max-frequency:
>>> +    minimum: 2105000
>>> +    maximum: 2850000
>>> +
>>> +  "#address-cells":
>>> +    const: 1
>>> +
>>> +  "#size-cells":
>>> +    const: 0
>>> +
>>> +patternProperties:
>>> +  "^multi-led@[0-9a-f]+$":
>>> +    type: object
>>> +    $ref: leds-class-multicolor.yaml#
>>> +    unevaluatedProperties: false
>>> +
>>> +    properties:
>>> +      color-index:
>>> +        description: |
>>> +          A 3-item array specifying color of each components in this LED. It
>>> +          should be one of the LED_COLOR_ID_* prefixed definitions from the
>>> +          header include/dt-bindings/leds/common.h. Defaults to
>>> +          <LED_COLOR_ID_GREEN LED_COLOR_ID_RED LED_COLOR_ID_BLUE>
>>> +          if unspecified.
>>> +        $ref: /schemas/types.yaml#/definitions/uint32-array
>>> +        maxItems: 3
>>
>> In general I am fine with it, although there is still question for
>> adding more multi-color defines in binding headers to replace this
>> property - GRB/RBG/GBR and even more for RGBW.
>>
>> Pavel, Lee, any thoughts from your side?
> 
> This really needs to mention the name this hardware is known as -- I
> believe it is NeoPixel.

We wait here for feedback on colors... The binding is re-implementing
color, just because of combinations GRB/RBG/GBR, which could be achieved
with new color defines.

Best regards,
Krzysztof