linux/drivers/leds/ledtrig-cpu.c
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   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
  33struct led_trigger_cpu {
  34        char name[MAX_NAME_LEN];
  35        struct led_trigger *_trig;
  36};
  37
  38static 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 */
  47void ledtrig_cpu(enum cpu_led_event ledevt)
  48{
  49        struct led_trigger_cpu *trig = &__get_cpu_var(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}
  71EXPORT_SYMBOL(ledtrig_cpu);
  72
  73static int ledtrig_cpu_syscore_suspend(void)
  74{
  75        ledtrig_cpu(CPU_LED_STOP);
  76        return 0;
  77}
  78
  79static void ledtrig_cpu_syscore_resume(void)
  80{
  81        ledtrig_cpu(CPU_LED_START);
  82}
  83
  84static void ledtrig_cpu_syscore_shutdown(void)
  85{
  86        ledtrig_cpu(CPU_LED_HALTED);
  87}
  88
  89static 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
  95static int __init ledtrig_cpu_init(void)
  96{
  97        int cpu;
  98
  99        /* Supports up to 9999 cpu cores */
 100        BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);
 101
 102        /*
 103         * Registering CPU led trigger for each CPU core here
 104         * ignores CPU hotplug, but after this CPU hotplug works
 105         * fine with this trigger.
 106         */
 107        for_each_possible_cpu(cpu) {
 108                struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
 109
 110                snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu);
 111
 112                led_trigger_register_simple(trig->name, &trig->_trig);
 113        }
 114
 115        register_syscore_ops(&ledtrig_cpu_syscore_ops);
 116
 117        pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");
 118
 119        return 0;
 120}
 121module_init(ledtrig_cpu_init);
 122
 123static void __exit ledtrig_cpu_exit(void)
 124{
 125        int cpu;
 126
 127        for_each_possible_cpu(cpu) {
 128                struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);
 129
 130                led_trigger_unregister_simple(trig->_trig);
 131                trig->_trig = NULL;
 132                memset(trig->name, 0, MAX_NAME_LEN);
 133        }
 134
 135        unregister_syscore_ops(&ledtrig_cpu_syscore_ops);
 136}
 137module_exit(ledtrig_cpu_exit);
 138
 139MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
 140MODULE_AUTHOR("Bryan Wu <bryan.wu@canonical.com>");
 141MODULE_DESCRIPTION("CPU LED trigger");
 142MODULE_LICENSE("GPL");
 143
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