ledtrig-transient.c

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/*
 * LED Kernel Transient Trigger
 *
 * Copyright (C) 2012 Shuah Khan <[email protected]>
 *
 * Based on Richard Purdie's ledtrig-timer.c and Atsushi Nemoto's
 * ledtrig-heartbeat.c
 * Design and use-case input from Jonas Bonn <[email protected]> and
 * Neil Brown <[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.
 *
 */
/*
 * Transient trigger allows one shot timer activation. Please refer to
 * Documentation/leds/ledtrig-transient.txt for details
*/

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/timer.h>
#include <linux/leds.h>
#include "leds.h"

struct transient_trig_data {
    int activate;
    int state;
    int restore_state;
    unsigned long duration;
    struct timer_list timer;
};

static void transient_timer_function(unsigned long data)
{
    struct led_classdev *led_cdev = (struct led_classdev *) data;
    struct transient_trig_data *transient_data = led_cdev->trigger_data;

    transient_data->activate = 0;
    __led_set_brightness(led_cdev, transient_data->restore_state);
}

static ssize_t transient_activate_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    struct led_classdev *led_cdev = dev_get_drvdata(dev);
    struct transient_trig_data *transient_data = led_cdev->trigger_data;

    return sprintf(buf, "%d\n", transient_data->activate);
}

static ssize_t transient_activate_store(struct device *dev,
        struct device_attribute *attr, const char *buf, size_t size)
{
    struct led_classdev *led_cdev = dev_get_drvdata(dev);
    struct transient_trig_data *transient_data = led_cdev->trigger_data;
    unsigned long state;
    ssize_t ret;

    ret = kstrtoul(buf, 10, &state);
    if (ret)
        return ret;

    if (state != 1 && state != 0)
        return -EINVAL;

    /* cancel the running timer */
    if (state == 0 && transient_data->activate == 1) {
        del_timer(&transient_data->timer);
        transient_data->activate = state;
        __led_set_brightness(led_cdev, transient_data->restore_state);
        return size;
    }

    /* start timer if there is no active timer */
    if (state == 1 && transient_data->activate == 0 &&
        transient_data->duration != 0) {
        transient_data->activate = state;
        __led_set_brightness(led_cdev, transient_data->state);
        transient_data->restore_state =
            (transient_data->state == LED_FULL) ? LED_OFF : LED_FULL;
        mod_timer(&transient_data->timer,
              jiffies + transient_data->duration);
    }

    /* state == 0 && transient_data->activate == 0
        timer is not active - just return */
    /* state == 1 && transient_data->activate == 1
        timer is already active - just return */

    return size;
}

static ssize_t transient_duration_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    struct led_classdev *led_cdev = dev_get_drvdata(dev);
    struct transient_trig_data *transient_data = led_cdev->trigger_data;

    return sprintf(buf, "%lu\n", transient_data->duration);
}

static ssize_t transient_duration_store(struct device *dev,
        struct device_attribute *attr, const char *buf, size_t size)
{
    struct led_classdev *led_cdev = dev_get_drvdata(dev);
    struct transient_trig_data *transient_data = led_cdev->trigger_data;
    unsigned long state;
    ssize_t ret;

    ret = kstrtoul(buf, 10, &state);
    if (ret)
        return ret;

    transient_data->duration = state;
    return size;
}

static ssize_t transient_state_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    struct led_classdev *led_cdev = dev_get_drvdata(dev);
    struct transient_trig_data *transient_data = led_cdev->trigger_data;
    int state;

    state = (transient_data->state == LED_FULL) ? 1 : 0;
    return sprintf(buf, "%d\n", state);
}

static ssize_t transient_state_store(struct device *dev,
        struct device_attribute *attr, const char *buf, size_t size)
{
    struct led_classdev *led_cdev = dev_get_drvdata(dev);
    struct transient_trig_data *transient_data = led_cdev->trigger_data;
    unsigned long state;
    ssize_t ret;

    ret = kstrtoul(buf, 10, &state);
    if (ret)
        return ret;

    if (state != 1 && state != 0)
        return -EINVAL;

    transient_data->state = (state == 1) ? LED_FULL : LED_OFF;
    return size;
}

static DEVICE_ATTR(activate, 0644, transient_activate_show,
           transient_activate_store);
static DEVICE_ATTR(duration, 0644, transient_duration_show,
           transient_duration_store);
static DEVICE_ATTR(state, 0644, transient_state_show, transient_state_store);

static void transient_trig_activate(struct led_classdev *led_cdev)
{
    int rc;
    struct transient_trig_data *tdata;

    tdata = kzalloc(sizeof(struct transient_trig_data), GFP_KERNEL);
    if (!tdata) {
        dev_err(led_cdev->dev,
            "unable to allocate transient trigger\n");
        return;
    }
    led_cdev->trigger_data = tdata;

    rc = device_create_file(led_cdev->dev, &dev_attr_activate);
    if (rc)
        goto err_out;

    rc = device_create_file(led_cdev->dev, &dev_attr_duration);
    if (rc)
        goto err_out_duration;

    rc = device_create_file(led_cdev->dev, &dev_attr_state);
    if (rc)
        goto err_out_state;

    setup_timer(&tdata->timer, transient_timer_function,
            (unsigned long) led_cdev);
    led_cdev->activated = true;

    return;

err_out_state:
    device_remove_file(led_cdev->dev, &dev_attr_duration);
err_out_duration:
    device_remove_file(led_cdev->dev, &dev_attr_activate);
err_out:
    dev_err(led_cdev->dev, "unable to register transient trigger\n");
    led_cdev->trigger_data = NULL;
    kfree(tdata);
}

static void transient_trig_deactivate(struct led_classdev *led_cdev)
{
    struct transient_trig_data *transient_data = led_cdev->trigger_data;

    if (led_cdev->activated) {
        del_timer_sync(&transient_data->timer);
        __led_set_brightness(led_cdev, transient_data->restore_state);
        device_remove_file(led_cdev->dev, &dev_attr_activate);
        device_remove_file(led_cdev->dev, &dev_attr_duration);
        device_remove_file(led_cdev->dev, &dev_attr_state);
        led_cdev->trigger_data = NULL;
        led_cdev->activated = false;
        kfree(transient_data);
    }
}

static struct led_trigger transient_trigger = {
    .name     = "transient",
    .activate = transient_trig_activate,
    .deactivate = transient_trig_deactivate,
};

static int __init transient_trig_init(void)
{
    return led_trigger_register(&transient_trigger);
}

static void __exit transient_trig_exit(void)
{
    led_trigger_unregister(&transient_trigger);
}

module_init(transient_trig_init);
module_exit(transient_trig_exit);

MODULE_AUTHOR("Shuah Khan <[email protected]>");
MODULE_DESCRIPTION("Transient LED trigger");
MODULE_LICENSE("GPL");