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/kernel.h>
  23 #include <linux/init.h>
  24 #include <linux/slab.h>
  25 #include <linux/percpu.h>
  26 #include <linux/syscore_ops.h>
  27 #include <linux/rwsem.h>
  28 #include <linux/cpu.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 };
  37
  38 static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);
  39
  40 /**
  41  * ledtrig_cpu - emit a CPU event as a trigger
  42  * @evt: CPU event to be emitted
  43  *
  44  * Emit a CPU event on a CPU core, which will trigger a
  45  * binded LED to turn on or turn off.
  46  */
  47 void ledtrig_cpu(enum cpu_led_event ledevt)
  48 {
  49         struct led_trigger_cpu *trig = this_cpu_ptr(&cpu_trig);
  50
  51         /* Locate the correct CPU LED */
  52         switch (ledevt) {
  53         case CPU_LED_IDLE_END:
  54         case CPU_LED_START:
  55                 /* Will turn the LED on, max brightness */
  56                 led_trigger_event(trig->_trig, LED_FULL);
  57                 break;
  58
  59         case CPU_LED_IDLE_START:
  60         case CPU_LED_STOP:
  61         case CPU_LED_HALTED:
  62                 /* Will turn the LED off */
  63                 led_trigger_event(trig->_trig, LED_OFF);
  64                 break;
  65
  66         default:
  67                 /* Will leave the LED as it is */
  68                 break;
  69         }
  70 }
  71 EXPORT_SYMBOL(ledtrig_cpu);
  72
  73 static int ledtrig_cpu_syscore_suspend(void)
  74 {
  75         ledtrig_cpu(CPU_LED_STOP);
  76         return 0;
  77 }
  78
  79 static void ledtrig_cpu_syscore_resume(void)
  80 {
  81         ledtrig_cpu(CPU_LED_START);
  82 }
  83
  84 static void ledtrig_cpu_syscore_shutdown(void)
  85 {
  86         ledtrig_cpu(CPU_LED_HALTED);
  87 }
  88
  89 static struct syscore_ops ledtrig_cpu_syscore_ops = {
  90         .shutdown       = ledtrig_cpu_syscore_shutdown,
  91         .suspend        = ledtrig_cpu_syscore_suspend,
  92         .resume         = ledtrig_cpu_syscore_resume,
  93 };
  94
  95 static int ledtrig_cpu_notify(struct notifier_block *self,
  96                                            unsigned long action, void *hcpu)
  97 {
  98         switch (action & ~CPU_TASKS_FROZEN) {
  99         case CPU_STARTING:
 100                 ledtrig_cpu(CPU_LED_START);
 101                 break;
 102         case CPU_DYING:
 103                 ledtrig_cpu(CPU_LED_STOP);
 104                 break;
 105         }
 106
 107         return NOTIFY_OK;
 108 }
 109
 110
 111 static struct notifier_block ledtrig_cpu_nb = {
 112         .notifier_call = ledtrig_cpu_notify,
 113 };
 114
 115 static int __init ledtrig_cpu_init(void)
 116 {
 117         int cpu;
 118
 119         /* Supports up to 9999 cpu cores */
 120         BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
 121
 122         /*
 123          * Registering CPU led trigger for each CPU core here
 124          * ignores CPU hotplug, but after this CPU hotplug works
 125          * fine with this trigger.
 126          */
 127         for_each_possible_cpu(cpu) {
 128                 struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
 129
 130                 snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
 131
 132                 led_trigger_register_simple(trig->name, &trig->_trig);
 133         }
 134
 135         register_syscore_ops(&ledtrig_cpu_syscore_ops);
 136         register_cpu_notifier(&ledtrig_cpu_nb);
 137
 138         pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
 139
 140         return 0;
 141 }
 142 device_initcall(ledtrig_cpu_init);