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1// SPDX-License-Identifier: GPL-2.02// Copyright (c) 2019 Christian Mauderer <oss@c-mauderer.de>3 4/*5 * The driver supports controllers with a very simple SPI protocol:6 * - one LED is controlled by a single byte on MOSI7 * - the value of the byte gives the brightness between two values (lowest to8 * highest)9 * - no return value is necessary (no MISO signal)10 *11 * The value for minimum and maximum brightness depends on the device12 * (compatible string).13 *14 * Supported devices:15 * - "ubnt,acb-spi-led": Microcontroller (SONiX 8F26E611LA) based device used16 * for example in Ubiquiti airCube ISP. Reverse engineered protocol for this17 * controller:18 * * Higher two bits set a mode. Lower six bits are a parameter.19 * * Mode: 00 -> set brightness between 0x00 (min) and 0x3F (max)20 * * Mode: 01 -> pulsing pattern (min -> max -> min) with an interval. From21 * some tests, the period is about (50ms + 102ms * parameter). There is a22 * slightly different pattern starting from 0x10 (longer gap between the23 * pulses) but the time still follows that calculation.24 * * Mode: 10 -> same as 01 but with only a ramp from min to max. Again a25 * slight jump in the pattern at 0x10.26 * * Mode: 11 -> blinking (off -> 25% -> off -> 25% -> ...) with a period of27 * (105ms * parameter)28 * NOTE: This driver currently only supports mode 00.29 */30 31#include <linux/leds.h>32#include <linux/mod_devicetable.h>33#include <linux/module.h>34#include <linux/mutex.h>35#include <linux/property.h>36#include <linux/spi/spi.h>37#include <uapi/linux/uleds.h>38 39struct spi_byte_chipdef {40 /* SPI byte that will be send to switch the LED off */41 u8 off_value;42 /* SPI byte that will be send to switch the LED to maximum brightness */43 u8 max_value;44};45 46struct spi_byte_led {47 struct led_classdev ldev;48 struct spi_device *spi;49 char name[LED_MAX_NAME_SIZE];50 struct mutex mutex;51 const struct spi_byte_chipdef *cdef;52};53 54static const struct spi_byte_chipdef ubnt_acb_spi_led_cdef = {55 .off_value = 0x0,56 .max_value = 0x3F,57};58 59static int spi_byte_brightness_set_blocking(struct led_classdev *dev,60 enum led_brightness brightness)61{62 struct spi_byte_led *led = container_of(dev, struct spi_byte_led, ldev);63 u8 value;64 int ret;65 66 value = (u8) brightness + led->cdef->off_value;67 68 mutex_lock(&led->mutex);69 ret = spi_write(led->spi, &value, sizeof(value));70 mutex_unlock(&led->mutex);71 72 return ret;73}74 75static int spi_byte_probe(struct spi_device *spi)76{77 struct fwnode_handle *child __free(fwnode_handle) = NULL;78 struct device *dev = &spi->dev;79 struct spi_byte_led *led;80 struct led_init_data init_data = {};81 enum led_default_state state;82 int ret;83 84 if (device_get_child_node_count(dev) != 1) {85 dev_err(dev, "Device must have exactly one LED sub-node.");86 return -EINVAL;87 }88 89 led = devm_kzalloc(dev, sizeof(*led), GFP_KERNEL);90 if (!led)91 return -ENOMEM;92 93 ret = devm_mutex_init(dev, &led->mutex);94 if (ret)95 return ret;96 97 led->spi = spi;98 led->cdef = device_get_match_data(dev);99 led->ldev.brightness = LED_OFF;100 led->ldev.max_brightness = led->cdef->max_value - led->cdef->off_value;101 led->ldev.brightness_set_blocking = spi_byte_brightness_set_blocking;102 103 child = device_get_next_child_node(dev, NULL);104 105 state = led_init_default_state_get(child);106 if (state == LEDS_DEFSTATE_ON)107 led->ldev.brightness = led->ldev.max_brightness;108 spi_byte_brightness_set_blocking(&led->ldev,109 led->ldev.brightness);110 111 init_data.fwnode = child;112 init_data.devicename = "leds-spi-byte";113 init_data.default_label = ":";114 115 return devm_led_classdev_register_ext(dev, &led->ldev, &init_data);116}117 118static const struct of_device_id spi_byte_dt_ids[] = {119 { .compatible = "ubnt,acb-spi-led", .data = &ubnt_acb_spi_led_cdef },120 {}121};122MODULE_DEVICE_TABLE(of, spi_byte_dt_ids);123 124static struct spi_driver spi_byte_driver = {125 .probe = spi_byte_probe,126 .driver = {127 .name = KBUILD_MODNAME,128 .of_match_table = spi_byte_dt_ids,129 },130};131module_spi_driver(spi_byte_driver);132 133MODULE_AUTHOR("Christian Mauderer <oss@c-mauderer.de>");134MODULE_DESCRIPTION("single byte SPI LED driver");135MODULE_LICENSE("GPL v2");136MODULE_ALIAS("spi:leds-spi-byte");137