ledtrig-backlight.c

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/*
 * Backlight emulation LED trigger
 *
 * Copyright 2008 (C) Rodolfo Giometti <[email protected]>
 * Copyright 2008 (C) Eurotech S.p.A. <[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/slab.h>
#include <linux/init.h>
#include <linux/fb.h>
#include <linux/leds.h>
#include "leds.h"

#define BLANK       1
#define UNBLANK     0

struct bl_trig_notifier {
    struct led_classdev *led;
    int brightness;
    int old_status;
    struct notifier_block notifier;
    unsigned invert;
};

static int fb_notifier_callback(struct notifier_block *p,
                unsigned long event, void *data)
{
    struct bl_trig_notifier *n = container_of(p,
                    struct bl_trig_notifier, notifier);
    struct led_classdev *led = n->led;
    struct fb_event *fb_event = data;
    int *blank = fb_event->data;
    int new_status = *blank ? BLANK : UNBLANK;

    switch (event) {
    case FB_EVENT_BLANK :
        if (new_status == n->old_status)
            break;

        if ((n->old_status == UNBLANK) ^ n->invert) {
            n->brightness = led->brightness;
            __led_set_brightness(led, LED_OFF);
        } else {
            __led_set_brightness(led, n->brightness);
        }

        n->old_status = new_status;

        break;
    }

    return 0;
}

static ssize_t bl_trig_invert_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    struct led_classdev *led = dev_get_drvdata(dev);
    struct bl_trig_notifier *n = led->trigger_data;

    return sprintf(buf, "%u\n", n->invert);
}

static ssize_t bl_trig_invert_store(struct device *dev,
        struct device_attribute *attr, const char *buf, size_t num)
{
    struct led_classdev *led = dev_get_drvdata(dev);
    struct bl_trig_notifier *n = led->trigger_data;
    unsigned long invert;
    int ret;

    ret = strict_strtoul(buf, 10, &invert);
    if (ret < 0)
        return ret;

    if (invert > 1)
        return -EINVAL;

    n->invert = invert;

    /* After inverting, we need to update the LED. */
    if ((n->old_status == BLANK) ^ n->invert)
        __led_set_brightness(led, LED_OFF);
    else
        __led_set_brightness(led, n->brightness);

    return num;
}
static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store);

static void bl_trig_activate(struct led_classdev *led)
{
    int ret;

    struct bl_trig_notifier *n;

    n = kzalloc(sizeof(struct bl_trig_notifier), GFP_KERNEL);
    led->trigger_data = n;
    if (!n) {
        dev_err(led->dev, "unable to allocate backlight trigger\n");
        return;
    }

    ret = device_create_file(led->dev, &dev_attr_inverted);
    if (ret)
        goto err_invert;

    n->led = led;
    n->brightness = led->brightness;
    n->old_status = UNBLANK;
    n->notifier.notifier_call = fb_notifier_callback;

    ret = fb_register_client(&n->notifier);
    if (ret)
        dev_err(led->dev, "unable to register backlight trigger\n");
    led->activated = true;

    return;

err_invert:
    led->trigger_data = NULL;
    kfree(n);
}

static void bl_trig_deactivate(struct led_classdev *led)
{
    struct bl_trig_notifier *n =
        (struct bl_trig_notifier *) led->trigger_data;

    if (led->activated) {
        device_remove_file(led->dev, &dev_attr_inverted);
        fb_unregister_client(&n->notifier);
        kfree(n);
        led->activated = false;
    }
}

static struct led_trigger bl_led_trigger = {
    .name       = "backlight",
    .activate   = bl_trig_activate,
    .deactivate = bl_trig_deactivate
};

static int __init bl_trig_init(void)
{
    return led_trigger_register(&bl_led_trigger);
}

static void __exit bl_trig_exit(void)
{
    led_trigger_unregister(&bl_led_trigger);
}

module_init(bl_trig_init);
module_exit(bl_trig_exit);

MODULE_AUTHOR("Rodolfo Giometti <[email protected]>");
MODULE_DESCRIPTION("Backlight emulation LED trigger");
MODULE_LICENSE("GPL v2");