[PATCH v4 0/3] leds: add driver for SPI driven WorldSemi WS2812B RGB LEDs

[Chuanhong Guo]

This patch adds support for driving a chain of WS2812B LED chips
using SPI bus.

WorldSemi WS2812B is a individually addressable LED chip that
can be chained together and controlled individually using a
single wire. The chip recognize a long pulse as a bit of 1 and
a short pulse as a bit of 0. Host sends a continuous stream
of 24-bits color values, each LED chip takes the first 3 byte
it receives as its color value and passes the leftover bytes to
the next LED on the chain.

This driver simulates this protocol using SPI bus by sending
a long pulse as 3'b110 and a short pulse as 3'b100. The SPI
frequency needs to be 2.105MHz~2.85MHz for the timing to be
correct and the controller needs to transfer all the bytes
continuously.

Changes since v1:
various dt binding fixes
add support for default-brightness

Changes since v2:
more dt binding fixes
drop default-brightness and default-intensity

Changes since v3:
1. add more comments
2. rename reg to cascade
3. redo some line breaking
4. move duplicated pointer calculation into ws2812b_set_byte
5. reword error message
6. get ws2812b_priv from led cdev->dev->parent

Chuanhong Guo (3):
  dt-bindings: vendor-prefixes: add an entry for WorldSemi
  dt-bindings: leds: add worldsemi,ws2812b
  leds: add driver for SPI driven WorldSemi WS2812B RGB LEDs

 .../bindings/leds/worldsemi,ws2812b.yaml      | 116 +++++++++
 .../devicetree/bindings/vendor-prefixes.yaml  |   2 +
 drivers/leds/rgb/Kconfig                      |  11 +
 drivers/leds/rgb/Makefile                     |   1 +
 drivers/leds/rgb/leds-ws2812b.c               | 231 ++++++++++++++++++
 5 files changed, 361 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/worldsemi,ws2812b.yaml
 create mode 100644 drivers/leds/rgb/leds-ws2812b.c

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2.38.1