On 30/11/2022 09:36, Chuanhong Guo wrote: > Hi! > > On Wed, Nov 30, 2022 at 12:54 AM Krzysztof Kozlowski > <krzysztof.kozlowski@xxxxxxxxxx> wrote: >>> +description: | >>> + WorldSemi WS2812B is a individually addressable LED chip that can be chained >>> + together and controlled individually using a single wire. >>> + This driver simulates the protocol used by this LED chip with SPI bus. >> >> Drop references to Linux driver, unless important for the binding. > > I think the SPI part is important. (I'll explain it below.) What about: > > This binding describes a chain of WS2812B LEDs connected to the SPI MOSI pin. > > instead? OK > >>> + 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-spi >> >> Drop "-spi". Compatibles are not supposed to include bus information. >> The same for file name. > > WS2812B isn't a SPI chip. It's controlled with only a single wire and > can be driven > using anything that can produce a long and a short pulse meeting its timing > requirement. > This driver uses a SPI bus to send the pulses, but it can also be > controlled with > I2S and the PIO pins on a Raspberry Pi Pico. > This spi suffix is to distinguish it from other possible > implementations if someone > else submits a support with a different peripheral. And that's exactly what I said - the compatibles should not include bus information. The bus information comes from... the bus! > >> >>> + >>> + reg: >>> + description: The chip-select line on the SPI bus >> >> Drop description, it's obvious. > > OK. > >> >>> + maxItems: 1 >>> + >>> + spi-max-frequency: >>> + $ref: /schemas/types.yaml#/definitions/uint32 >>> + description: >>> + Maximum SPI clocking speed of the device in Hz. >> >> No need for ref and description. It comes from spi-peripheral-props. > > OK. > >> >>> + minimum: 2105000 >>> + maximum: 2850000 >>> + >>> + "#address-cells": >>> + const: 1 >>> + >>> + "#size-cells": >>> + const: 0 >>> + >>> +patternProperties: >>> + "^multi-led(@[0-9a-f])?$": >> >> 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. > >> >>> + type: object >>> + $ref: leds-class-multicolor.yaml# >> >> unevaluatedProperties: false > > OK. > >>> + >>> + 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 >>> + minItems: 3 >> >> Drop minItems.... but see comment below: >> >>> + maxItems: 3 >> >> Why this is different than other multi-color LEDs? I would expect here >> children with common.yaml. > > WS2812B is a single LED package with 3 diodes and a microcontroller. > Each LED package has 3 colors. The original chip comes with GRB > color while there are some clones with RGB arrangement instead. > The LED chain can be really long so I'd like to simplify the binding > by using a single property to override the only variable, color, here. OK, that makes sense. > >> >>> + >>> + 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 >> >> Drop minItems.... but: >> >>> + maxItems: 3 >>> + items: >>> + minimum: 0 >>> + maximum: 255 >> >> default: 255 >> >> What controls the intensity? Don't you have PWM there? > > The LED takes 3-byte brightness value of each color. This property is used to > specify the default multi_intensity field for the multi-color LED. The final > brightness value is calculated with led_mc_calc_color_components like this: > > mcled_cdev->subled_info[i].brightness = brightness * > mcled_cdev->subled_info[i].intensity / led_cdev->max_brightness; > > The LED chip takes exactly 8 bits for the brightness (max_brightness = 255 > which can't be changed.), so according to the formula above the maximum > intensity should be 255. So this is brightness of each color... why insisting on calling it differently? Best regards, Krzysztof
