// SPDX-License-Identifier: GPL-2.0

/*
 * LED pattern trigger
 *
 * Idea discussed with Pavel Machek. Raphael Teysseyre implemented
 * the first version, Baolin Wang simplified and improved the approach.
 */

#include <linux/kernel.h>
#include <linux/leds.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/timer.h>

#define MAX_PATTERNS            1024
/*
 * When doing gradual dimming, the led brightness will be updated
 * every 50 milliseconds.
 */
#define UPDATE_INTERVAL         50

struct pattern_trig_data {
        struct led_classdev *led_cdev;
        struct led_pattern patterns[MAX_PATTERNS];
        struct led_pattern *curr;
        struct led_pattern *next;
        struct mutex lock;
        u32 npatterns;
        int repeat;
        int last_repeat;
        int delta_t;
        bool is_indefinite;
        bool is_hw_pattern;
        struct timer_list timer;
};

static void pattern_trig_update_patterns(struct pattern_trig_data *data)
{
        data->curr = data->next;
        if (!data->is_indefinite && data->curr == data->patterns)
                data->repeat--;

        if (data->next == data->patterns + data->npatterns - 1)
                data->next = data->patterns;
        else
                data->next++;

        data->delta_t = 0;
}

static int pattern_trig_compute_brightness(struct pattern_trig_data *data)
{
        int step_brightness;

        /*
         * If current tuple's duration is less than the dimming interval,
         * we should treat it as a step change of brightness instead of
         * doing gradual dimming.
         */
        if (data->delta_t == 0 || data->curr->delta_t < UPDATE_INTERVAL)
                return data->curr->brightness;

        step_brightness = abs(data->next->brightness - data->curr->brightness);
        step_brightness = data->delta_t * step_brightness / data->curr->delta_t;

        if (data->next->brightness > data->curr->brightness)
                return data->curr->brightness + step_brightness;
        else
                return data->curr->brightness - step_brightness;
}

static void pattern_trig_timer_function(struct timer_list *t)
{
        struct pattern_trig_data *data = from_timer(data, t, timer);

        for (;;) {
                if (!data->is_indefinite && !data->repeat)
                        break;

                if (data->curr->brightness == data->next->brightness) {
                        /* Step change of brightness */
                        led_set_brightness(data->led_cdev,
                                           data->curr->brightness);
                        mod_timer(&data->timer,
                                  jiffies + msecs_to_jiffies(data->curr->delta_t));
                        if (!data->next->delta_t) {
                                /* Skip the tuple with zero duration */
                                pattern_trig_update_patterns(data);
                        }
                        /* Select next tuple */
                        pattern_trig_update_patterns(data);
                } else {
                        /* Gradual dimming */

                        /*
                         * If the accumulation time is larger than current
                         * tuple's duration, we should go next one and re-check
                         * if we repeated done.
                         */
                        if (data->delta_t > data->curr->delta_t) {
                                pattern_trig_update_patterns(data);
                                continue;
                        }

                        led_set_brightness(data->led_cdev,
                                           pattern_trig_compute_brightness(data));
                        mod_timer(&data->timer,
                                  jiffies + msecs_to_jiffies(UPDATE_INTERVAL));

                        /* Accumulate the gradual dimming time */
                        data->delta_t += UPDATE_INTERVAL;
                }

                break;
        }
}

static int pattern_trig_start_pattern(struct led_classdev *led_cdev)
{
        struct pattern_trig_data *data = led_cdev->trigger_data;

        if (!data->npatterns)
                return 0;

        if (data->is_hw_pattern) {
                return led_cdev->pattern_set(led_cdev, data->patterns,
                                             data->npatterns, data->repeat);
        }

        /* At least 2 tuples for software pattern. */
        if (data->npatterns < 2)
                return -EINVAL;

        data->delta_t = 0;
        data->curr = data->patterns;
        data->next = data->patterns + 1;
        data->timer.expires = jiffies;
        add_timer(&data->timer);

        return 0;
}

static ssize_t repeat_show(struct device *dev, struct device_attribute *attr,
                           char *buf)
{
        struct led_classdev *led_cdev = dev_get_drvdata(dev);
        struct pattern_trig_data *data = led_cdev->trigger_data;
        int repeat;

        mutex_lock(&data->lock);

        repeat = data->last_repeat;

        mutex_unlock(&data->lock);

        return scnprintf(buf, PAGE_SIZE, "%d\n", repeat);
}

static ssize_t repeat_store(struct device *dev, struct device_attribute *attr,
                            const char *buf, size_t count)
{
        struct led_classdev *led_cdev = dev_get_drvdata(dev);
        struct pattern_trig_data *data = led_cdev->trigger_data;
        int err, res;

        err = kstrtos32(buf, 10, &res);
        if (err)
                return err;

        /* Number 0 and negative numbers except -1 are invalid. */
        if (res < -1 || res == 0)
                return -EINVAL;

        mutex_lock(&data->lock);

        del_timer_sync(&data->timer);

        if (data->is_hw_pattern)
                led_cdev->pattern_clear(led_cdev);

        data->last_repeat = data->repeat = res;
        /* -1 means repeat indefinitely */
        if (data->repeat == -1)
                data->is_indefinite = true;
        else
                data->is_indefinite = false;

        err = pattern_trig_start_pattern(led_cdev);

        mutex_unlock(&data->lock);
        return err < 0 ? err : count;
}

static DEVICE_ATTR_RW(repeat);

static ssize_t pattern_trig_show_patterns(struct pattern_trig_data *data,
                                          char *buf, bool hw_pattern)
{
        ssize_t count = 0;
        int i;

        mutex_lock(&data->lock);

        if (!data->npatterns || (data->is_hw_pattern ^ hw_pattern))
                goto out;

        for (i = 0; i < data->npatterns; i++) {
                count += scnprintf(buf + count, PAGE_SIZE - count,
                                   "%d %u ",
                                   data->patterns[i].brightness,
                                   data->patterns[i].delta_t);
        }

        buf[count - 1] = '\n';

out:
        mutex_unlock(&data->lock);
        return count;
}

static ssize_t pattern_trig_store_patterns(struct led_classdev *led_cdev,
                                           const char *buf, size_t count,
                                           bool hw_pattern)
{
        struct pattern_trig_data *data = led_cdev->trigger_data;
        int ccount, cr, offset = 0, err = 0;

        mutex_lock(&data->lock);

        del_timer_sync(&data->timer);

        if (data->is_hw_pattern)
                led_cdev->pattern_clear(led_cdev);

        data->is_hw_pattern = hw_pattern;
        data->npatterns = 0;

        while (offset < count - 1 && data->npatterns < MAX_PATTERNS) {
                cr = 0;
                ccount = sscanf(buf + offset, "%d %u %n",
                                &data->patterns[data->npatterns].brightness,
                                &data->patterns[data->npatterns].delta_t, &cr);
                if (ccount != 2) {
                        data->npatterns = 0;
                        err = -EINVAL;
                        goto out;
                }

                offset += cr;
                data->npatterns++;
        }

        err = pattern_trig_start_pattern(led_cdev);
        if (err)
                data->npatterns = 0;

out:
        mutex_unlock(&data->lock);
        return err < 0 ? err : count;
}

static ssize_t pattern_show(struct device *dev, struct device_attribute *attr,
                            char *buf)
{
        struct led_classdev *led_cdev = dev_get_drvdata(dev);
        struct pattern_trig_data *data = led_cdev->trigger_data;

        return pattern_trig_show_patterns(data, buf, false);
}

static ssize_t pattern_store(struct device *dev, struct device_attribute *attr,
                             const char *buf, size_t count)
{
        struct led_classdev *led_cdev = dev_get_drvdata(dev);

        return pattern_trig_store_patterns(led_cdev, buf, count, false);
}

static DEVICE_ATTR_RW(pattern);

static ssize_t hw_pattern_show(struct device *dev,
                               struct device_attribute *attr, char *buf)
{
        struct led_classdev *led_cdev = dev_get_drvdata(dev);
        struct pattern_trig_data *data = led_cdev->trigger_data;

        return pattern_trig_show_patterns(data, buf, true);
}

static ssize_t hw_pattern_store(struct device *dev,
                                struct device_attribute *attr,
                                const char *buf, size_t count)
{
        struct led_classdev *led_cdev = dev_get_drvdata(dev);

        return pattern_trig_store_patterns(led_cdev, buf, count, true);
}

static DEVICE_ATTR_RW(hw_pattern);

static umode_t pattern_trig_attrs_mode(struct kobject *kobj,
                                       struct attribute *attr, int index)
{
        struct device *dev = container_of(kobj, struct device, kobj);
        struct led_classdev *led_cdev = dev_get_drvdata(dev);

        if (attr == &dev_attr_repeat.attr || attr == &dev_attr_pattern.attr)
                return attr->mode;
        else if (attr == &dev_attr_hw_pattern.attr && led_cdev->pattern_set)
                return attr->mode;

        return 0;
}

static struct attribute *pattern_trig_attrs[] = {
        &dev_attr_pattern.attr,
        &dev_attr_hw_pattern.attr,
        &dev_attr_repeat.attr,
        NULL
};

static const struct attribute_group pattern_trig_group = {
        .attrs = pattern_trig_attrs,
        .is_visible = pattern_trig_attrs_mode,
};

static const struct attribute_group *pattern_trig_groups[] = {
        &pattern_trig_group,
        NULL,
};

static int pattern_trig_activate(struct led_classdev *led_cdev)
{
        struct pattern_trig_data *data;

        data = kzalloc(sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        if (!!led_cdev->pattern_set ^ !!led_cdev->pattern_clear) {
                dev_warn(led_cdev->dev,
                         "Hardware pattern ops validation failed\n");
                led_cdev->pattern_set = NULL;
                led_cdev->pattern_clear = NULL;
        }

        data->is_indefinite = true;
        data->last_repeat = -1;
        mutex_init(&data->lock);
        data->led_cdev = led_cdev;
        led_set_trigger_data(led_cdev, data);
        timer_setup(&data->timer, pattern_trig_timer_function, 0);
        led_cdev->activated = true;

        return 0;
}

static void pattern_trig_deactivate(struct led_classdev *led_cdev)
{
        struct pattern_trig_data *data = led_cdev->trigger_data;

        if (!led_cdev->activated)
                return;

        if (led_cdev->pattern_clear)
                led_cdev->pattern_clear(led_cdev);

        del_timer_sync(&data->timer);

        led_set_brightness(led_cdev, LED_OFF);
        kfree(data);
        led_cdev->activated = false;
}

static struct led_trigger pattern_led_trigger = {
        .name = "pattern",
        .activate = pattern_trig_activate,
        .deactivate = pattern_trig_deactivate,
        .groups = pattern_trig_groups,
};

static int __init pattern_trig_init(void)
{
        return led_trigger_register(&pattern_led_trigger);
}

static void __exit pattern_trig_exit(void)
{
        led_trigger_unregister(&pattern_led_trigger);
}

module_init(pattern_trig_init);
module_exit(pattern_trig_exit);

MODULE_AUTHOR("Raphael Teysseyre <rteysseyre@gmail.com");
MODULE_AUTHOR("Baolin Wang <baolin.wang@linaro.org");
MODULE_DESCRIPTION("LED Pattern trigger");
MODULE_LICENSE("GPL v2");