text: // SPDX-License-Identifier: GPL-2.0
  //
  // LED Kernel Transient Trigger
  //
  // Transient trigger allows one shot timer activation. Please refer to
  // Documentation/leds/ledtrig-transient.txt for details
  // Copyright (C) 2012 Shuah Khan <shuahkhan@gmail.com>
  //
  // Based on Richard Purdie's ledtrig-timer.c and Atsushi Nemoto's
  // ledtrig-heartbeat.c
  // Design and use-case input from Jonas Bonn <jonas@southpole.se> and
  // Neil Brown <neilb@suse.de>
  
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/device.h>
  #include <linux/slab.h>
  #include <linux/timer.h>
  #include <linux/leds.h>
  #include "../leds.h"
  
  struct transient_trig_data {
  	int activate;
  	int state;
  	int restore_state;
  	unsigned long duration;
  	struct timer_list timer;
  	struct led_classdev *led_cdev;
  };
  
  static void transient_timer_function(struct timer_list *t)
  {
  	struct transient_trig_data *transient_data =
  		from_timer(transient_data, t, timer);
  	struct led_classdev *led_cdev = transient_data->led_cdev;
  
  	transient_data->activate = 0;
  	led_set_brightness_nosleep(led_cdev, transient_data->restore_state);
  }
  
  static ssize_t transient_activate_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct transient_trig_data *transient_data =
  		led_trigger_get_drvdata(dev);
  
  	return sprintf(buf, "%d\n", transient_data->activate);
  }
  
  static ssize_t transient_activate_store(struct device *dev,
  		struct device_attribute *attr, const char *buf, size_t size)
  {
  	struct led_classdev *led_cdev = led_trigger_get_led(dev);
  	struct transient_trig_data *transient_data =
  		led_trigger_get_drvdata(dev);
  	unsigned long state;
  	ssize_t ret;
  
  	ret = kstrtoul(buf, 10, &state);
  	if (ret)
  		return ret;
  
  	if (state != 1 && state != 0)
  		return -EINVAL;
  
  	/* cancel the running timer */
  	if (state == 0 && transient_data->activate == 1) {
  		del_timer(&transient_data->timer);
  		transient_data->activate = state;
  		led_set_brightness_nosleep(led_cdev,
  					transient_data->restore_state);
  		return size;
  	}
  
  	/* start timer if there is no active timer */
  	if (state == 1 && transient_data->activate == 0 &&
  	    transient_data->duration != 0) {
  		transient_data->activate = state;
  		led_set_brightness_nosleep(led_cdev, transient_data->state);
  		transient_data->restore_state =
  		    (transient_data->state == LED_FULL) ? LED_OFF : LED_FULL;
  		mod_timer(&transient_data->timer,
  			  jiffies + msecs_to_jiffies(transient_data->duration));
  	}
  
  	/* state == 0 && transient_data->activate == 0
  		timer is not active - just return */
  	/* state == 1 && transient_data->activate == 1
  		timer is already active - just return */
  
  	return size;
  }
  
  static ssize_t transient_duration_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct transient_trig_data *transient_data = led_trigger_get_drvdata(dev);
  
  	return sprintf(buf, "%lu\n", transient_data->duration);
  }
  
  static ssize_t transient_duration_store(struct device *dev,
  		struct device_attribute *attr, const char *buf, size_t size)
  {
  	struct transient_trig_data *transient_data =
  		led_trigger_get_drvdata(dev);
  	unsigned long state;
  	ssize_t ret;
  
  	ret = kstrtoul(buf, 10, &state);
  	if (ret)
  		return ret;
  
  	transient_data->duration = state;
  	return size;
  }
  
  static ssize_t transient_state_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct transient_trig_data *transient_data =
  		led_trigger_get_drvdata(dev);
  	int state;
  
  	state = (transient_data->state == LED_FULL) ? 1 : 0;
  	return sprintf(buf, "%d\n", state);
  }
  
  static ssize_t transient_state_store(struct device *dev,
  		struct device_attribute *attr, const char *buf, size_t size)
  {
  	struct transient_trig_data *transient_data =
  		led_trigger_get_drvdata(dev);
  	unsigned long state;
  	ssize_t ret;
  
  	ret = kstrtoul(buf, 10, &state);
  	if (ret)
  		return ret;
  
  	if (state != 1 && state != 0)
  		return -EINVAL;
  
  	transient_data->state = (state == 1) ? LED_FULL : LED_OFF;
  	return size;
  }
  
  static DEVICE_ATTR(activate, 0644, transient_activate_show,
  		   transient_activate_store);
  static DEVICE_ATTR(duration, 0644, transient_duration_show,
  		   transient_duration_store);
  static DEVICE_ATTR(state, 0644, transient_state_show, transient_state_store);
  
  static struct attribute *transient_trig_attrs[] = {
  	&dev_attr_activate.attr,
  	&dev_attr_duration.attr,
  	&dev_attr_state.attr,
  	NULL
  };
  ATTRIBUTE_GROUPS(transient_trig);
  
  static int transient_trig_activate(struct led_classdev *led_cdev)
  {
  	struct transient_trig_data *tdata;
  
  	tdata = kzalloc(sizeof(struct transient_trig_data), GFP_KERNEL);
  	if (!tdata)
  		return -ENOMEM;
  
  	led_set_trigger_data(led_cdev, tdata);
  	tdata->led_cdev = led_cdev;
  
  	timer_setup(&tdata->timer, transient_timer_function, 0);
  
  	return 0;
  }
  
  static void transient_trig_deactivate(struct led_classdev *led_cdev)
  {
  	struct transient_trig_data *transient_data = led_get_trigger_data(led_cdev);
  
  	del_timer_sync(&transient_data->timer);
  	led_set_brightness_nosleep(led_cdev, transient_data->restore_state);
  	kfree(transient_data);
  }
  
  static struct led_trigger transient_trigger = {
  	.name     = "transient",
  	.activate = transient_trig_activate,
  	.deactivate = transient_trig_deactivate,
  	.groups = transient_trig_groups,
  };
  module_led_trigger(transient_trigger);
  
  MODULE_AUTHOR("Shuah Khan <shuahkhan@gmail.com>");
  MODULE_DESCRIPTION("Transient LED trigger");
  MODULE_LICENSE("GPL v2");
  