ledtrig-cpu.c

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/*
 * 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 <[email protected]>
 * Copyright 2011 - 2012 Bryan Wu <[email protected]>
 *
 * 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/module.h>
#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 "leds.h"

#define MAX_NAME_LEN    8

struct led_trigger_cpu {
    char name[MAX_NAME_LEN];
    struct led_trigger *_trig;
};

static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);

void ledtrig_cpu(enum cpu_led_event ledevt)
{
    struct led_trigger_cpu *trig = &__get_cpu_var(cpu_trig);

    /* Locate the correct CPU LED */
    switch (ledevt) {
    case CPU_LED_IDLE_END:
    case CPU_LED_START:
        /* Will turn the LED on, max brightness */
        led_trigger_event(trig->_trig, LED_FULL);
        break;

    case CPU_LED_IDLE_START:
    case CPU_LED_STOP:
    case CPU_LED_HALTED:
        /* Will turn the LED off */
        led_trigger_event(trig->_trig, LED_OFF);
        break;

    default:
        /* Will leave the LED as it is */
        break;
    }
}
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 __init ledtrig_cpu_init(void)
{
    int cpu;

    /* Supports up to 9999 cpu cores */
    BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);

    /*
     * 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);

    pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");

    return 0;
}
module_init(ledtrig_cpu_init);

static void __exit ledtrig_cpu_exit(void)
{
    int cpu;

    for_each_possible_cpu(cpu) {
        struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);

        led_trigger_unregister_simple(trig->_trig);
        trig->_trig = NULL;
        memset(trig->name, 0, MAX_NAME_LEN);
    }

    unregister_syscore_ops(&ledtrig_cpu_syscore_ops);
}
module_exit(ledtrig_cpu_exit);

MODULE_AUTHOR("Linus Walleij <[email protected]>");
MODULE_AUTHOR("Bryan Wu <[email protected]>");
MODULE_DESCRIPTION("CPU LED trigger");
MODULE_LICENSE("GPL");