drivers/leds/ledtrig-cpu.c

   1 /*
   2  * ledtrig-cpu.c - LED trigger based on CPU activity
   3  *
   4  * This LED trigger will be registered for each possible CPU and named as
   5  * cpu0, cpu1, cpu2, cpu3, etc.
   6  *
   7  * It can be bound to any LED just like other triggers using either a
   8  * board file or via sysfs interface.
   9  *
  10  * An API named ledtrig_cpu is exported for any user, who want to add CPU
  11  * activity indication in their code
  12  *
  13  * Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
  14  * Copyright 2011 - 2012 Bryan Wu <bryan.wu@canonical.com>
  15  *
  16  * This program is free software; you can redistribute it and/or modify
  17  * it under the terms of the GNU General Public License version 2 as
  18  * published by the Free Software Foundation.
  19  *
  20  */
  21
  22 #include <linux/module.h>
  23 #include <linux/kernel.h>
  24 #include <linux/init.h>
  25 #include <linux/slab.h>
  26 #include <linux/percpu.h>
  27 #include <linux/syscore_ops.h>
  28 #include <linux/rwsem.h>
  29 #include "leds.h"
  30
  31 #define MAX_NAME_LEN    8
  32
  33 struct led_trigger_cpu {
  34         char name[MAX_NAME_LEN];
  35         struct led_trigger *_trig;
  36         struct mutex lock;
  37         int lock_is_inited;
  38 };
  39
  40 static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);
  41
  42 /**
  43  * ledtrig_cpu - emit a CPU event as a trigger
  44  * @evt: CPU event to be emitted
  45  *
  46  * Emit a CPU event on a CPU core, which will trigger a
  47  * binded LED to turn on or turn off.
  48  */
  49 void ledtrig_cpu(enum cpu_led_event ledevt)
  50 {
  51         struct led_trigger_cpu *trig = &__get_cpu_var(cpu_trig);
  52
  53         /* mutex lock should be initialized before calling mutex_call() */
  54         if (!trig->lock_is_inited)
  55                 return;
  56
  57         mutex_lock(&trig->lock);
  58
  59         /* Locate the correct CPU LED */
  60         switch (ledevt) {
  61         case CPU_LED_IDLE_END:
  62         case CPU_LED_START:
  63                 /* Will turn the LED on, max brightness */
  64                 led_trigger_event(trig->_trig, LED_FULL);
  65                 break;
  66
  67         case CPU_LED_IDLE_START:
  68         case CPU_LED_STOP:
  69         case CPU_LED_HALTED:
  70                 /* Will turn the LED off */
  71                 led_trigger_event(trig->_trig, LED_OFF);
  72                 break;
  73
  74         default:
  75                 /* Will leave the LED as it is */
  76                 break;
  77         }
  78
  79         mutex_unlock(&trig->lock);
  80 }
  81 EXPORT_SYMBOL(ledtrig_cpu);
  82
  83 static int ledtrig_cpu_syscore_suspend(void)
  84 {
  85         ledtrig_cpu(CPU_LED_STOP);
  86         return 0;
  87 }
  88
  89 static void ledtrig_cpu_syscore_resume(void)
  90 {
  91         ledtrig_cpu(CPU_LED_START);
  92 }
  93
  94 static void ledtrig_cpu_syscore_shutdown(void)
  95 {
  96         ledtrig_cpu(CPU_LED_HALTED);
  97 }
  98
  99 static struct syscore_ops ledtrig_cpu_syscore_ops = {
 100         .shutdown       = ledtrig_cpu_syscore_shutdown,
 101         .suspend        = ledtrig_cpu_syscore_suspend,
 102         .resume         = ledtrig_cpu_syscore_resume,
 103 };
 104
 105 static int __init ledtrig_cpu_init(void)
 106 {
 107         int cpu;
 108
 109         /* Supports up to 9999 cpu cores */
 110         BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
 111
 112         /*
 113          * Registering CPU led trigger for each CPU core here
 114          * ignores CPU hotplug, but after this CPU hotplug works
 115          * fine with this trigger.
 116          */
 117         for_each_possible_cpu(cpu) {
 118                 struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
 119
 120                 mutex_init(&trig->lock);
 121
 122                 snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
 123
 124                 mutex_lock(&trig->lock);
 125                 led_trigger_register_simple(trig->name, &trig->_trig);
 126                 trig->lock_is_inited = 1;
 127                 mutex_unlock(&trig->lock);
 128         }
 129
 130         register_syscore_ops(&ledtrig_cpu_syscore_ops);
 131
 132         pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
 133
 134         return 0;
 135 }
 136 module_init(ledtrig_cpu_init);
 137
 138 static void __exit ledtrig_cpu_exit(void)
 139 {
 140         int cpu;
 141
 142         for_each_possible_cpu(cpu) {
 143                 struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
 144
 145                 mutex_lock(&trig->lock);
 146
 147                 led_trigger_unregister_simple(trig->_trig);
 148                 trig->_trig = NULL;
 149                 memset(trig->name, 0, MAX_NAME_LEN);
 150                 trig->lock_is_inited = 0;
 151
 152                 mutex_unlock(&trig->lock);
 153                 mutex_destroy(&trig->lock);
 154         }
 155
 156         unregister_syscore_ops(&ledtrig_cpu_syscore_ops);
 157 }
 158 module_exit(ledtrig_cpu_exit);
 159
 160 MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
 161 MODULE_AUTHOR("Bryan Wu <bryan.wu@canonical.com>");
 162 MODULE_DESCRIPTION("CPU LED trigger");
 163 MODULE_LICENSE("GPL");