kernel: add driver package for WS2812B LEDs
Two WS2812B (NeoPixel) clones are used in Xiaomi Redmi AX6000 as indicator lights. Add a driver for controlling it using SPI MOSI. Signed-off-by: Chuanhong Guo <gch981213@gmail.com>
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Chuanhong Guo
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#
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# Copyright (C) 2008-2010 OpenWrt.org
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#
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# This is free software, licensed under the GNU General Public License v2.
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# See /LICENSE for more information.
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#
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include $(TOPDIR)/rules.mk
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include $(INCLUDE_DIR)/kernel.mk
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PKG_NAME:=leds-ws2812b
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PKG_RELEASE:=1
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PKG_LICENSE:=GPL-2.0
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include $(INCLUDE_DIR)/package.mk
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define KernelPackage/leds-ws2812b
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SUBMENU:=LED modules
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TITLE:=Worldsemi WS2812B (NeoPixel) LED support
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FILES:= \
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$(PKG_BUILD_DIR)/leds-ws2812b.ko
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AUTOLOAD:=$(call AutoProbe,leds-ws2812b,1)
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DEPENDS:=@TARGET_mediatek_filogic
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endef
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define KernelPackage/leds-ws2812b/description
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LED support for driving WS2812B (NeoPixel) using SPI MOSI.
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endef
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define Build/Compile
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$(KERNEL_MAKE) M="$(PKG_BUILD_DIR)" modules
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endef
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$(eval $(call KernelPackage,leds-ws2812b))
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obj-m := leds-ws2812b.o
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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* WorldSemi WS2812B individually-addressable LED driver using SPI
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*
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* Copyright 2022 Chuanhong Guo <gch981213@gmail.com>
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*
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* This driver simulates WS2812B protocol using SPI MOSI pin. A one pulse
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* is transferred as 3'b110 and a zero pulse is 3'b100. For this driver to
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* work properly, the SPI frequency should be 2.105MHz~2.85MHz and it needs
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* to transfer all the bytes continuously.
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*/
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#include <linux/led-class-multicolor.h>
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#include <linux/leds.h>
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#include <linux/module.h>
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#include <linux/of_device.h>
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#include <linux/property.h>
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#include <linux/spi/spi.h>
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#include <linux/mutex.h>
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#define WS2812B_BYTES_PER_COLOR 3
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#define WS2812B_NUM_COLORS 3
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/* A continuous 0 for 50us+ as the 'reset' signal */
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#define WS2812B_RESET_LEN 18
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struct ws2812b_led {
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struct led_classdev_mc mc_cdev;
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struct mc_subled subled[WS2812B_NUM_COLORS];
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int cascade;
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};
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struct ws2812b_priv {
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struct led_classdev ldev;
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struct spi_device *spi;
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struct mutex mutex;
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int num_leds;
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size_t data_len;
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u8 *data_buf;
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struct ws2812b_led leds[];
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};
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/**
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* ws2812b_set_byte - convert a byte of data to 3-byte SPI data for pulses
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* @priv: pointer to the private data structure
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* @offset: offset of the target byte in the data stream
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* @val: 1-byte data to be set
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*
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* WS2812B receives a stream of bytes from DI, takes the first 3 byte as LED
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* brightness and pases the rest to the next LED through the DO pin.
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* This function assembles a single byte of data to the LED:
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* A bit is represented with a pulse of specific length. A long pulse is a 1
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* and a short pulse is a 0.
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* SPI transfers data continuously, MSB first. We can send 3'b100 to create a
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* 0 pulse and 3'b110 for a 1 pulse. In this way, a byte of data takes up 3
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* bytes in a SPI transfer:
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* 1x0 1x0 1x0 1x0 1x0 1x0 1x0 1x0
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* Let's rearrange it in 8 bits:
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* 1x01x01x 01x01x01 x01x01x0
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* The higher 3 bits, middle 2 bits and lower 3 bits are represented with the
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* 1st, 2nd and 3rd byte in the SPI transfer respectively.
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* There are only 8 combinations for 3 bits and 4 for 2 bits, so we can create
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* a lookup table for the 3 bytes.
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* e.g. For 0x6b -> 2'b01101011:
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* Bit 7-5: 3'b011 -> 10011011 -> 0x9b
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* Bit 4-3: 2'b01 -> 01001101 -> 0x4d
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* Bit 2-0: 3'b011 -> 00110110 -> 0x36
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*/
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static void ws2812b_set_byte(struct ws2812b_priv *priv, size_t offset, u8 val)
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{
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/* The lookup table for Bit 7-5 4-3 2-0 */
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const u8 h3b[] = { 0x92, 0x93, 0x9a, 0x9b, 0xd2, 0xd3, 0xda, 0xdb };
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const u8 m2b[] = { 0x49, 0x4d, 0x69, 0x6d };
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const u8 l3b[] = { 0x24, 0x26, 0x34, 0x36, 0xa4, 0xa6, 0xb4, 0xb6 };
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u8 *p = priv->data_buf + WS2812B_RESET_LEN + (offset * WS2812B_BYTES_PER_COLOR);
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p[0] = h3b[val >> 5]; /* Bit 7-5 */
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p[1] = m2b[(val >> 3) & 0x3]; /* Bit 4-3 */
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p[2] = l3b[val & 0x7]; /* Bit 2-0 */
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}
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static int ws2812b_set(struct led_classdev *cdev,
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enum led_brightness brightness)
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{
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struct led_classdev_mc *mc_cdev = lcdev_to_mccdev(cdev);
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struct ws2812b_led *led =
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container_of(mc_cdev, struct ws2812b_led, mc_cdev);
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struct ws2812b_priv *priv = dev_get_drvdata(cdev->dev->parent);
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int ret;
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int i;
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led_mc_calc_color_components(mc_cdev, brightness);
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mutex_lock(&priv->mutex);
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for (i = 0; i < WS2812B_NUM_COLORS; i++)
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ws2812b_set_byte(priv, led->cascade * WS2812B_NUM_COLORS + i,
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led->subled[i].brightness);
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ret = spi_write(priv->spi, priv->data_buf, priv->data_len);
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mutex_unlock(&priv->mutex);
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return ret;
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}
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static int ws2812b_probe(struct spi_device *spi)
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{
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struct device *dev = &spi->dev;
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int cur_led = 0;
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struct ws2812b_priv *priv;
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struct fwnode_handle *led_node;
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int num_leds, i, cnt, ret;
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num_leds = device_get_child_node_count(dev);
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priv = devm_kzalloc(dev, struct_size(priv, leds, num_leds), GFP_KERNEL);
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if (!priv)
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return -ENOMEM;
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priv->data_len =
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num_leds * WS2812B_BYTES_PER_COLOR * WS2812B_NUM_COLORS +
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WS2812B_RESET_LEN;
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priv->data_buf = kzalloc(priv->data_len, GFP_KERNEL);
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if (!priv->data_buf)
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return -ENOMEM;
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for (i = 0; i < num_leds * WS2812B_NUM_COLORS; i++)
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ws2812b_set_byte(priv, i, 0);
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mutex_init(&priv->mutex);
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priv->num_leds = num_leds;
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priv->spi = spi;
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device_for_each_child_node(dev, led_node) {
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struct led_init_data init_data = {
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.fwnode = led_node,
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};
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/* WS2812B LEDs usually come with GRB color */
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u32 color_idx[WS2812B_NUM_COLORS] = {
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LED_COLOR_ID_GREEN,
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LED_COLOR_ID_RED,
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LED_COLOR_ID_BLUE,
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};
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u32 cascade;
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ret = fwnode_property_read_u32(led_node, "reg", &cascade);
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if (ret) {
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dev_err(dev, "failed to obtain numerical LED index for %s",
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fwnode_get_name(led_node));
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goto ERR_UNREG_LEDS;
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}
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if (cascade >= num_leds) {
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dev_err(dev, "LED index of %s is larger than the number of LEDs.",
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fwnode_get_name(led_node));
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ret = -EINVAL;
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goto ERR_UNREG_LEDS;
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}
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cnt = fwnode_property_count_u32(led_node, "color-index");
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if (cnt > 0 && cnt <= WS2812B_NUM_COLORS)
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fwnode_property_read_u32_array(led_node, "color-index",
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color_idx, (size_t)cnt);
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priv->leds[cur_led].mc_cdev.subled_info =
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priv->leds[cur_led].subled;
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priv->leds[cur_led].mc_cdev.num_colors = WS2812B_NUM_COLORS;
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priv->leds[cur_led].mc_cdev.led_cdev.max_brightness = 255;
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priv->leds[cur_led].mc_cdev.led_cdev.brightness_set_blocking = ws2812b_set;
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for (i = 0; i < WS2812B_NUM_COLORS; i++) {
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priv->leds[cur_led].subled[i].color_index = color_idx[i];
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priv->leds[cur_led].subled[i].intensity = 255;
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}
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priv->leds[cur_led].cascade = cascade;
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ret = led_classdev_multicolor_register_ext(
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dev, &priv->leds[cur_led].mc_cdev, &init_data);
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if (ret) {
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dev_err(dev, "registration of %s failed.",
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fwnode_get_name(led_node));
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goto ERR_UNREG_LEDS;
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}
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cur_led++;
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}
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spi_set_drvdata(spi, priv);
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return 0;
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ERR_UNREG_LEDS:
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for (; cur_led >= 0; cur_led--)
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led_classdev_multicolor_unregister(&priv->leds[cur_led].mc_cdev);
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mutex_destroy(&priv->mutex);
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kfree(priv->data_buf);
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return ret;
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}
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static int ws2812b_remove(struct spi_device *spi)
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{
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struct ws2812b_priv *priv = spi_get_drvdata(spi);
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int cur_led;
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for (cur_led = priv->num_leds - 1; cur_led >= 0; cur_led--)
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led_classdev_multicolor_unregister(&priv->leds[cur_led].mc_cdev);
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kfree(priv->data_buf);
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mutex_destroy(&priv->mutex);
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return 0;
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}
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static const struct spi_device_id ws2812b_spi_ids[] = {
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{ "ws2812b" },
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{},
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};
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MODULE_DEVICE_TABLE(spi, ws2812b_spi_ids);
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static const struct of_device_id ws2812b_dt_ids[] = {
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{ .compatible = "worldsemi,ws2812b" },
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{},
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};
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MODULE_DEVICE_TABLE(of, ws2812b_dt_ids);
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static struct spi_driver ws2812b_driver = {
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.probe = ws2812b_probe,
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.remove = ws2812b_remove,
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.id_table = ws2812b_spi_ids,
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.driver = {
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.name = KBUILD_MODNAME,
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.of_match_table = ws2812b_dt_ids,
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},
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};
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module_spi_driver(ws2812b_driver);
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MODULE_AUTHOR("Chuanhong Guo <gch981213@gmail.com>");
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MODULE_DESCRIPTION("WS2812B LED driver using SPI");
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MODULE_LICENSE("GPL");
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