/*
   * 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 <linux/slab.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
  ", 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
  ");
  		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, "%u
  ", gpio_data->inverted);
  }
  
  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 long inverted;
  	int ret;
  
  	ret = kstrtoul(buf, 10, &inverted);
  	if (ret < 0)
  		return ret;
  
  	if (inverted > 1)
  		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
  ", 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
  ");
  		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
  ", 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);
  	led->activated = true;
  
  	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 (led->activated) {
  		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);
  		led->activated = false;
  	}
  }
  
  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");