LXR linux/drivers/leds/leds-spi-byte.c

   1// SPDX-License-Identifier: GPL-2.0
   2// 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 MOSI
   7 * - the value of the byte gives the brightness between two values (lowest to
   8 *   highest)
   9 * - no return value is necessary (no MISO signal)
  10 *
  11 * The value for minimum and maximum brightness depends on the device
  12 * (compatible string).
  13 *
  14 * Supported devices:
  15 * - "ubnt,acb-spi-led": Microcontroller (SONiX 8F26E611LA) based device used
  16 *   for example in Ubiquiti airCube ISP. Reverse engineered protocol for this
  17 *   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. From
  21 *     some tests, the period is about (50ms + 102ms * parameter). There is a
  22 *     slightly different pattern starting from 0x10 (longer gap between the
  23 *     pulses) but the time still follows that calculation.
  24 *   * Mode: 10 -> same as 01 but with only a ramp from min to max. Again a
  25 *     slight jump in the pattern at 0x10.
  26 *   * Mode: 11 -> blinking (off -> 25% -> off -> 25% -> ...) with a period of
  27 *     (105ms * parameter)
  28 *   NOTE: This driver currently only supports mode 00.
  29 */
  30
  31#include <linux/leds.h>
  32#include <linux/module.h>
  33#include <linux/of_device.h>
  34#include <linux/spi/spi.h>
  35#include <linux/mutex.h>
  36#include <uapi/linux/uleds.h>
  37
  38struct spi_byte_chipdef {
  39        /* SPI byte that will be send to switch the LED off */
  40        u8      off_value;
  41        /* SPI byte that will be send to switch the LED to maximum brightness */
  42        u8      max_value;
  43};
  44
  45struct spi_byte_led {
  46        struct led_classdev             ldev;
  47        struct spi_device               *spi;
  48        char                            name[LED_MAX_NAME_SIZE];
  49        struct mutex                    mutex;
  50        const struct spi_byte_chipdef   *cdef;
  51};
  52
  53static const struct spi_byte_chipdef ubnt_acb_spi_led_cdef = {
  54        .off_value = 0x0,
  55        .max_value = 0x3F,
  56};
  57
  58static const struct of_device_id spi_byte_dt_ids[] = {
  59        { .compatible = "ubnt,acb-spi-led", .data = &ubnt_acb_spi_led_cdef },
  60        {},
  61};
  62
  63MODULE_DEVICE_TABLE(of, spi_byte_dt_ids);
  64
  65static int spi_byte_brightness_set_blocking(struct led_classdev *dev,
  66                                            enum led_brightness brightness)
  67{
  68        struct spi_byte_led *led = container_of(dev, struct spi_byte_led, ldev);
  69        u8 value;
  70        int ret;
  71
  72        value = (u8) brightness + led->cdef->off_value;
  73
  74        mutex_lock(&led->mutex);
  75        ret = spi_write(led->spi, &value, sizeof(value));
  76        mutex_unlock(&led->mutex);
  77
  78        return ret;
  79}
  80
  81static int spi_byte_probe(struct spi_device *spi)
  82{
  83        const struct of_device_id *of_dev_id;
  84        struct device_node *child;
  85        struct device *dev = &spi->dev;
  86        struct spi_byte_led *led;
  87        const char *name = "leds-spi-byte::";
  88        const char *state;
  89        int ret;
  90
  91        of_dev_id = of_match_device(spi_byte_dt_ids, dev);
  92        if (!of_dev_id)
  93                return -EINVAL;
  94
  95        if (of_get_child_count(dev->of_node) != 1) {
  96                dev_err(dev, "Device must have exactly one LED sub-node.");
  97                return -EINVAL;
  98        }
  99        child = of_get_next_child(dev->of_node, NULL);
 100
 101        led = devm_kzalloc(dev, sizeof(*led), GFP_KERNEL);
 102        if (!led)
 103                return -ENOMEM;
 104
 105        of_property_read_string(child, "label", &name);
 106        strlcpy(led->name, name, sizeof(led->name));
 107        led->spi = spi;
 108        mutex_init(&led->mutex);
 109        led->cdef = of_dev_id->data;
 110        led->ldev.name = led->name;
 111        led->ldev.brightness = LED_OFF;
 112        led->ldev.max_brightness = led->cdef->max_value - led->cdef->off_value;
 113        led->ldev.brightness_set_blocking = spi_byte_brightness_set_blocking;
 114
 115        state = of_get_property(child, "default-state", NULL);
 116        if (state) {
 117                if (!strcmp(state, "on")) {
 118                        led->ldev.brightness = led->ldev.max_brightness;
 119                } else if (strcmp(state, "off")) {
 120                        /* all other cases except "off" */
 121                        dev_err(dev, "default-state can only be 'on' or 'off'");
 122                        return -EINVAL;
 123                }
 124        }
 125        spi_byte_brightness_set_blocking(&led->ldev,
 126                                         led->ldev.brightness);
 127
 128        ret = devm_led_classdev_register(&spi->dev, &led->ldev);
 129        if (ret) {
 130                mutex_destroy(&led->mutex);
 131                return ret;
 132        }
 133        spi_set_drvdata(spi, led);
 134
 135        return 0;
 136}
 137
 138static int spi_byte_remove(struct spi_device *spi)
 139{
 140        struct spi_byte_led     *led = spi_get_drvdata(spi);
 141
 142        mutex_destroy(&led->mutex);
 143
 144        return 0;
 145}
 146
 147static struct spi_driver spi_byte_driver = {
 148        .probe          = spi_byte_probe,
 149        .remove         = spi_byte_remove,
 150        .driver = {
 151                .name           = KBUILD_MODNAME,
 152                .of_match_table = spi_byte_dt_ids,
 153        },
 154};
 155
 156module_spi_driver(spi_byte_driver);
 157
 158MODULE_AUTHOR("Christian Mauderer <oss@c-mauderer.de>");
 159MODULE_DESCRIPTION("single byte SPI LED driver");
 160MODULE_LICENSE("GPL v2");
 161MODULE_ALIAS("spi:leds-spi-byte");
 162