text: /*
   * ledtrig-cpu.c - LED trigger based on CPU activity
   *
   * This LED trigger will be registered for each possible CPU and named as
   * cpu0, cpu1, cpu2, cpu3, etc.
   *
   * It can be bound to any LED just like other triggers using either a
   * board file or via sysfs interface.
   *
   * An API named ledtrig_cpu is exported for any user, who want to add CPU
   * activity indication in their code
   *
   * Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
   * Copyright 2011 - 2012 Bryan Wu <bryan.wu@canonical.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/kernel.h>
  #include <linux/init.h>
  #include <linux/slab.h>
  #include <linux/percpu.h>
  #include <linux/syscore_ops.h>
  #include <linux/rwsem.h>
  #include <linux/cpu.h>
  #include "../leds.h"
  
  #define MAX_NAME_LEN	8
  
  struct led_trigger_cpu {
  	bool is_active;
  	char name[MAX_NAME_LEN];
  	struct led_trigger *_trig;
  };
  
  static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);
  
  static struct led_trigger *trig_cpu_all;
  static atomic_t num_active_cpus = ATOMIC_INIT(0);
  
  /**
   * ledtrig_cpu - emit a CPU event as a trigger
   * @evt: CPU event to be emitted
   *
   * Emit a CPU event on a CPU core, which will trigger a
   * bound LED to turn on or turn off.
   */
  void ledtrig_cpu(enum cpu_led_event ledevt)
  {
  	struct led_trigger_cpu *trig = this_cpu_ptr(&cpu_trig);
  	bool is_active = trig->is_active;
  
  	/* Locate the correct CPU LED */
  	switch (ledevt) {
  	case CPU_LED_IDLE_END:
  	case CPU_LED_START:
  		/* Will turn the LED on, max brightness */
  		is_active = true;
  		break;
  
  	case CPU_LED_IDLE_START:
  	case CPU_LED_STOP:
  	case CPU_LED_HALTED:
  		/* Will turn the LED off */
  		is_active = false;
  		break;
  
  	default:
  		/* Will leave the LED as it is */
  		break;
  	}
  
  	if (is_active != trig->is_active) {
  		unsigned int active_cpus;
  		unsigned int total_cpus;
  
  		/* Update trigger state */
  		trig->is_active = is_active;
  		atomic_add(is_active ? 1 : -1, &num_active_cpus);
  		active_cpus = atomic_read(&num_active_cpus);
  		total_cpus = num_present_cpus();
  
  		led_trigger_event(trig->_trig,
  			is_active ? LED_FULL : LED_OFF);
  
  
  		led_trigger_event(trig_cpu_all,
  			DIV_ROUND_UP(LED_FULL * active_cpus, total_cpus));
  
  	}
  }
  EXPORT_SYMBOL(ledtrig_cpu);
  
  static int ledtrig_cpu_syscore_suspend(void)
  {
  	ledtrig_cpu(CPU_LED_STOP);
  	return 0;
  }
  
  static void ledtrig_cpu_syscore_resume(void)
  {
  	ledtrig_cpu(CPU_LED_START);
  }
  
  static void ledtrig_cpu_syscore_shutdown(void)
  {
  	ledtrig_cpu(CPU_LED_HALTED);
  }
  
  static struct syscore_ops ledtrig_cpu_syscore_ops = {
  	.shutdown	= ledtrig_cpu_syscore_shutdown,
  	.suspend	= ledtrig_cpu_syscore_suspend,
  	.resume		= ledtrig_cpu_syscore_resume,
  };
  
  static int ledtrig_online_cpu(unsigned int cpu)
  {
  	ledtrig_cpu(CPU_LED_START);
  	return 0;
  }
  
  static int ledtrig_prepare_down_cpu(unsigned int cpu)
  {
  	ledtrig_cpu(CPU_LED_STOP);
  	return 0;
  }
  
  static int __init ledtrig_cpu_init(void)
  {
  	int cpu;
  	int ret;
  
  	/* Supports up to 9999 cpu cores */
  	BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
  
  	/*
  	 * Registering a trigger for all CPUs.
  	 */
  	led_trigger_register_simple("cpu", &trig_cpu_all);
  
  	/*
  	 * Registering CPU led trigger for each CPU core here
  	 * ignores CPU hotplug, but after this CPU hotplug works
  	 * fine with this trigger.
  	 */
  	for_each_possible_cpu(cpu) {
  		struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
  
  		snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
  
  		led_trigger_register_simple(trig->name, &trig->_trig);
  	}
  
  	register_syscore_ops(&ledtrig_cpu_syscore_ops);
  
  	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "leds/trigger:starting",
  				ledtrig_online_cpu, ledtrig_prepare_down_cpu);
  	if (ret < 0)
  		pr_err("CPU hotplug notifier for ledtrig-cpu could not be registered: %d\n",
  		       ret);
  
  	pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
  
  	return 0;
  }
  device_initcall(ledtrig_cpu_init);
  