// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2019 Christian Mauderer <oss@c-mauderer.de>

/*
 * The driver supports controllers with a very simple SPI protocol:
 * - one LED is controlled by a single byte on MOSI
 * - the value of the byte gives the brightness between two values (lowest to
 *   highest)
 * - no return value is necessary (no MISO signal)
 *
 * The value for minimum and maximum brightness depends on the device
 * (compatible string).
 *
 * Supported devices:
 * - "ubnt,acb-spi-led": Microcontroller (SONiX 8F26E611LA) based device used
 *   for example in Ubiquiti airCube ISP. Reverse engineered protocol for this
 *   controller:
 *   * Higher two bits set a mode. Lower six bits are a parameter.
 *   * Mode: 00 -> set brightness between 0x00 (min) and 0x3F (max)
 *   * Mode: 01 -> pulsing pattern (min -> max -> min) with an interval. From
 *     some tests, the period is about (50ms + 102ms * parameter). There is a
 *     slightly different pattern starting from 0x10 (longer gap between the
 *     pulses) but the time still follows that calculation.
 *   * Mode: 10 -> same as 01 but with only a ramp from min to max. Again a
 *     slight jump in the pattern at 0x10.
 *   * Mode: 11 -> blinking (off -> 25% -> off -> 25% -> ...) with a period of
 *     (105ms * parameter)
 *   NOTE: This driver currently only supports mode 00.
 */

#include <linux/leds.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/property.h>
#include <linux/spi/spi.h>
#include <uapi/linux/uleds.h>

struct spi_byte_chipdef {
        /* SPI byte that will be send to switch the LED off */
        u8      off_value;
        /* SPI byte that will be send to switch the LED to maximum brightness */
        u8      max_value;
};

struct spi_byte_led {
        struct led_classdev             ldev;
        struct spi_device               *spi;
        char                            name[LED_MAX_NAME_SIZE];
        struct mutex                    mutex;
        const struct spi_byte_chipdef   *cdef;
};

static const struct spi_byte_chipdef ubnt_acb_spi_led_cdef = {
        .off_value = 0x0,
        .max_value = 0x3F,
};

static int spi_byte_brightness_set_blocking(struct led_classdev *dev,
                                            enum led_brightness brightness)
{
        struct spi_byte_led *led = container_of(dev, struct spi_byte_led, ldev);
        u8 value;
        int ret;

        value = (u8) brightness + led->cdef->off_value;

        mutex_lock(&led->mutex);
        ret = spi_write(led->spi, &value, sizeof(value));
        mutex_unlock(&led->mutex);

        return ret;
}

static int spi_byte_probe(struct spi_device *spi)
{
        struct fwnode_handle *child __free(fwnode_handle) = NULL;
        struct device *dev = &spi->dev;
        struct spi_byte_led *led;
        struct led_init_data init_data = {};
        enum led_default_state state;
        int ret;

        if (device_get_child_node_count(dev) != 1) {
                dev_err(dev, "Device must have exactly one LED sub-node.");
                return -EINVAL;
        }

        led = devm_kzalloc(dev, sizeof(*led), GFP_KERNEL);
        if (!led)
                return -ENOMEM;

        ret = devm_mutex_init(dev, &led->mutex);
        if (ret)
                return ret;

        led->spi = spi;
        led->cdef = device_get_match_data(dev);
        led->ldev.brightness = LED_OFF;
        led->ldev.max_brightness = led->cdef->max_value - led->cdef->off_value;
        led->ldev.brightness_set_blocking = spi_byte_brightness_set_blocking;

        child = device_get_next_child_node(dev, NULL);

        state = led_init_default_state_get(child);
        if (state == LEDS_DEFSTATE_ON)
                led->ldev.brightness = led->ldev.max_brightness;
        spi_byte_brightness_set_blocking(&led->ldev,
                                         led->ldev.brightness);

        init_data.fwnode = child;
        init_data.devicename = "leds-spi-byte";
        init_data.default_label = ":";

        return devm_led_classdev_register_ext(dev, &led->ldev, &init_data);
}

static const struct of_device_id spi_byte_dt_ids[] = {
        { .compatible = "ubnt,acb-spi-led", .data = &ubnt_acb_spi_led_cdef },
        {}
};
MODULE_DEVICE_TABLE(of, spi_byte_dt_ids);

static struct spi_driver spi_byte_driver = {
        .probe          = spi_byte_probe,
        .driver = {
                .name           = KBUILD_MODNAME,
                .of_match_table = spi_byte_dt_ids,
        },
};
module_spi_driver(spi_byte_driver);

MODULE_AUTHOR("Christian Mauderer <oss@c-mauderer.de>");
MODULE_DESCRIPTION("single byte SPI LED driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("spi:leds-spi-byte");