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

Lee Jones
2023-01-09T16:54:06Z

On Sat, 24 Dec 2022, Krzysztof Kozlowski wrote:

> 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@gmail.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@gmail.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:

Why "index"?

Isn't it just an array of colours rather than an index into something?

> >>> + description: |
> >>> + A 3-item array specifying color of each components in this LED. It

Why are you forcing this to 3?

Surely there are multi-colour LEDs containing more or less colours?

> >>> + should be one of the LED_COLOR_ID_* prefixed definitions from the
> >>> + header include/dt-bindings/leds/common.h. Defaults to

Isn't "include" a Linuxisum?

> >>> + <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.

Sure, but where does that end?

How many permutations are there likely to be?

An unlimited array has more of a chance of standing the test of time.

--
Lee Jones [李琼斯]