drivers/leds/trigger/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 <linux/cpu.h>
  30 #include "../leds.h"
  31
  32 #define MAX_NAME_LEN    8
  33
  34 struct led_trigger_cpu {
  35         char name[MAX_NAME_LEN];
  36         struct led_trigger *_trig;
  37 };
  38
  39 static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);
  40
  41 /**
  42  * ledtrig_cpu - emit a CPU event as a trigger
  43  * @evt: CPU event to be emitted
  44  *
  45  * Emit a CPU event on a CPU core, which will trigger a
  46  * binded LED to turn on or turn off.
  47  */
  48 void ledtrig_cpu(enum cpu_led_event ledevt)
  49 {
  50         struct led_trigger_cpu *trig = this_cpu_ptr(&cpu_trig);
  51
  52         /* Locate the correct CPU LED */
  53         switch (ledevt) {
  54         case CPU_LED_IDLE_END:
  55         case CPU_LED_START:
  56                 /* Will turn the LED on, max brightness */
  57                 led_trigger_event(trig->_trig, LED_FULL);
  58                 break;
  59
  60         case CPU_LED_IDLE_START:
  61         case CPU_LED_STOP:
  62         case CPU_LED_HALTED:
  63                 /* Will turn the LED off */
  64                 led_trigger_event(trig->_trig, LED_OFF);
  65                 break;
  66
  67         default:
  68                 /* Will leave the LED as it is */
  69                 break;
  70         }
  71 }
  72 EXPORT_SYMBOL(ledtrig_cpu);
  73
  74 static int ledtrig_cpu_syscore_suspend(void)
  75 {
  76         ledtrig_cpu(CPU_LED_STOP);
  77         return 0;
  78 }
  79
  80 static void ledtrig_cpu_syscore_resume(void)
  81 {
  82         ledtrig_cpu(CPU_LED_START);
  83 }
  84
  85 static void ledtrig_cpu_syscore_shutdown(void)
  86 {
  87         ledtrig_cpu(CPU_LED_HALTED);
  88 }
  89
  90 static struct syscore_ops ledtrig_cpu_syscore_ops = {
  91         .shutdown       = ledtrig_cpu_syscore_shutdown,
  92         .suspend        = ledtrig_cpu_syscore_suspend,
  93         .resume         = ledtrig_cpu_syscore_resume,
  94 };
  95
  96 static int ledtrig_cpu_notify(struct notifier_block *self,
  97                                            unsigned long action, void *hcpu)
  98 {
  99         switch (action & ~CPU_TASKS_FROZEN) {
 100         case CPU_STARTING:
 101                 ledtrig_cpu(CPU_LED_START);
 102                 break;
 103         case CPU_DYING:
 104                 ledtrig_cpu(CPU_LED_STOP);
 105                 break;
 106         }
 107
 108         return NOTIFY_OK;
 109 }
 110
 111
 112 static struct notifier_block ledtrig_cpu_nb = {
 113         .notifier_call = ledtrig_cpu_notify,
 114 };
 115
 116 static int __init ledtrig_cpu_init(void)
 117 {
 118         int cpu;
 119
 120         /* Supports up to 9999 cpu cores */
 121         BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
 122
 123         /*
 124          * Registering CPU led trigger for each CPU core here
 125          * ignores CPU hotplug, but after this CPU hotplug works
 126          * fine with this trigger.
 127          */
 128         for_each_possible_cpu(cpu) {
 129                 struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
 130
 131                 snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
 132
 133                 led_trigger_register_simple(trig->name, &trig->_trig);
 134         }
 135
 136         register_syscore_ops(&ledtrig_cpu_syscore_ops);
 137         register_cpu_notifier(&ledtrig_cpu_nb);
 138
 139         pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
 140
 141         return 0;
 142 }
 143 module_init(ledtrig_cpu_init);
 144
 145 static void __exit ledtrig_cpu_exit(void)
 146 {
 147         int cpu;
 148
 149         unregister_cpu_notifier(&ledtrig_cpu_nb);
 150
 151         for_each_possible_cpu(cpu) {
 152                 struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
 153
 154                 led_trigger_unregister_simple(trig->_trig);
 155                 trig->_trig = NULL;
 156                 memset(trig->name, 0, MAX_NAME_LEN);
 157         }
 158
 159         unregister_syscore_ops(&ledtrig_cpu_syscore_ops);
 160 }
 161 module_exit(ledtrig_cpu_exit);
 162
 163 MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
 164 MODULE_AUTHOR("Bryan Wu <bryan.wu@canonical.com>");
 165 MODULE_DESCRIPTION("CPU LED trigger");
 166 MODULE_LICENSE("GPL");