/*
 * ledtrig-gio.c - LED Trigger Based on GPIO events
 *
 * Copyright 2009 Felipe Balbi <me@felipebalbi.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/gpio.h>
#include <linux/interrupt.h>
#include <linux/workqueue.h>
#include <linux/leds.h>
#include "leds.h"

struct gpio_trig_data {
        struct led_classdev *led;
        struct work_struct work;

        unsigned desired_brightness;    /* desired brightness when led is on */
        unsigned inverted;              /* true when gpio is inverted */
        unsigned gpio;                  /* gpio that triggers the leds */
};

static irqreturn_t gpio_trig_irq(int irq, void *_led)
{
        struct led_classdev *led = _led;
        struct gpio_trig_data *gpio_data = led->trigger_data;

        /* just schedule_work since gpio_get_value can sleep */
        schedule_work(&gpio_data->work);

        return IRQ_HANDLED;
};

static void gpio_trig_work(struct work_struct *work)
{
        struct gpio_trig_data *gpio_data = container_of(work,
                        struct gpio_trig_data, work);
        int tmp;

        if (!gpio_data->gpio)
                return;

        tmp = gpio_get_value(gpio_data->gpio);
        if (gpio_data->inverted)
                tmp = !tmp;

        if (tmp) {
                if (gpio_data->desired_brightness)
                        led_set_brightness(gpio_data->led,
                                           gpio_data->desired_brightness);
                else
                        led_set_brightness(gpio_data->led, LED_FULL);
        } else {
                led_set_brightness(gpio_data->led, LED_OFF);
        }
}

static ssize_t gpio_trig_brightness_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct led_classdev *led = dev_get_drvdata(dev);
        struct gpio_trig_data *gpio_data = led->trigger_data;

        return sprintf(buf, "%u\n", gpio_data->desired_brightness);
}

static ssize_t gpio_trig_brightness_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t n)
{
        struct led_classdev *led = dev_get_drvdata(dev);
        struct gpio_trig_data *gpio_data = led->trigger_data;
        unsigned desired_brightness;
        int ret;

        ret = sscanf(buf, "%u", &desired_brightness);
        if (ret < 1 || desired_brightness > 255) {
                dev_err(dev, "invalid value\n");
                return -EINVAL;
        }

        gpio_data->desired_brightness = desired_brightness;

        return n;
}
static DEVICE_ATTR(desired_brightness, 0644, gpio_trig_brightness_show,
                gpio_trig_brightness_store);

static ssize_t gpio_trig_inverted_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct led_classdev *led = dev_get_drvdata(dev);
        struct gpio_trig_data *gpio_data = led->trigger_data;

        return sprintf(buf, "%s\n", gpio_data->inverted ? "yes" : "no");
}

static ssize_t gpio_trig_inverted_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t n)
{
        struct led_classdev *led = dev_get_drvdata(dev);
        struct gpio_trig_data *gpio_data = led->trigger_data;
        unsigned inverted;
        int ret;

        ret = sscanf(buf, "%u", &inverted);
        if (ret < 1) {
                dev_err(dev, "invalid value\n");
                return -EINVAL;
        }

        gpio_data->inverted = !!inverted;

        /* After inverting, we need to update the LED. */
        schedule_work(&gpio_data->work);

        return n;
}
static DEVICE_ATTR(inverted, 0644, gpio_trig_inverted_show,
                gpio_trig_inverted_store);

static ssize_t gpio_trig_gpio_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct led_classdev *led = dev_get_drvdata(dev);
        struct gpio_trig_data *gpio_data = led->trigger_data;

        return sprintf(buf, "%u\n", gpio_data->gpio);
}

static ssize_t gpio_trig_gpio_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t n)
{
        struct led_classdev *led = dev_get_drvdata(dev);
        struct gpio_trig_data *gpio_data = led->trigger_data;
        unsigned gpio;
        int ret;

        ret = sscanf(buf, "%u", &gpio);
        if (ret < 1) {
                dev_err(dev, "couldn't read gpio number\n");
                flush_work(&gpio_data->work);
                return -EINVAL;
        }

        if (gpio_data->gpio == gpio)
                return n;

        if (!gpio) {
                if (gpio_data->gpio != 0)
                        free_irq(gpio_to_irq(gpio_data->gpio), led);
                gpio_data->gpio = 0;
                return n;
        }

        ret = request_irq(gpio_to_irq(gpio), gpio_trig_irq,
                        IRQF_SHARED | IRQF_TRIGGER_RISING
                        | IRQF_TRIGGER_FALLING, "ledtrig-gpio", led);
        if (ret) {
                dev_err(dev, "request_irq failed with error %d\n", ret);
        } else {
                if (gpio_data->gpio != 0)
                        free_irq(gpio_to_irq(gpio_data->gpio), led);
                gpio_data->gpio = gpio;
        }

        return ret ? ret : n;
}
static DEVICE_ATTR(gpio, 0644, gpio_trig_gpio_show, gpio_trig_gpio_store);

static void gpio_trig_activate(struct led_classdev *led)
{
        struct gpio_trig_data *gpio_data;
        int ret;

        gpio_data = kzalloc(sizeof(*gpio_data), GFP_KERNEL);
        if (!gpio_data)
                return;

        ret = device_create_file(led->dev, &dev_attr_gpio);
        if (ret)
                goto err_gpio;

        ret = device_create_file(led->dev, &dev_attr_inverted);
        if (ret)
                goto err_inverted;

        ret = device_create_file(led->dev, &dev_attr_desired_brightness);
        if (ret)
                goto err_brightness;

        gpio_data->led = led;
        led->trigger_data = gpio_data;
        INIT_WORK(&gpio_data->work, gpio_trig_work);

        return;

err_brightness:
        device_remove_file(led->dev, &dev_attr_inverted);

err_inverted:
        device_remove_file(led->dev, &dev_attr_gpio);

err_gpio:
        kfree(gpio_data);
}

static void gpio_trig_deactivate(struct led_classdev *led)
{
        struct gpio_trig_data *gpio_data = led->trigger_data;

        if (gpio_data) {
                device_remove_file(led->dev, &dev_attr_gpio);
                device_remove_file(led->dev, &dev_attr_inverted);
                device_remove_file(led->dev, &dev_attr_desired_brightness);
                flush_work(&gpio_data->work);
                if (gpio_data->gpio != 0)
                        free_irq(gpio_to_irq(gpio_data->gpio), led);
                kfree(gpio_data);
        }
}

static struct led_trigger gpio_led_trigger = {
        .name           = "gpio",
        .activate       = gpio_trig_activate,
        .deactivate     = gpio_trig_deactivate,
};

static int __init gpio_trig_init(void)
{
        return led_trigger_register(&gpio_led_trigger);
}
module_init(gpio_trig_init);

static void __exit gpio_trig_exit(void)
{
        led_trigger_unregister(&gpio_led_trigger);
}
module_exit(gpio_trig_exit);

MODULE_AUTHOR("Felipe Balbi <me@felipebalbi.com>");
MODULE_DESCRIPTION("GPIO LED trigger");
MODULE_LICENSE("GPL");