linux/drivers/leds/ledtrig-backlight.c
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   1/*
   2 * Backlight emulation LED trigger
   3 *
   4 * Copyright 2008 (C) Rodolfo Giometti <giometti@linux.it>
   5 * Copyright 2008 (C) Eurotech S.p.A. <info@eurotech.it>
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 as
   9 * published by the Free Software Foundation.
  10 *
  11 */
  12
  13#include <linux/module.h>
  14#include <linux/kernel.h>
  15#include <linux/slab.h>
  16#include <linux/init.h>
  17#include <linux/fb.h>
  18#include <linux/leds.h>
  19#include "leds.h"
  20
  21#define BLANK           1
  22#define UNBLANK         0
  23
  24struct bl_trig_notifier {
  25        struct led_classdev *led;
  26        int brightness;
  27        int old_status;
  28        struct notifier_block notifier;
  29};
  30
  31static int fb_notifier_callback(struct notifier_block *p,
  32                                unsigned long event, void *data)
  33{
  34        struct bl_trig_notifier *n = container_of(p,
  35                                        struct bl_trig_notifier, notifier);
  36        struct led_classdev *led = n->led;
  37        struct fb_event *fb_event = data;
  38        int *blank = fb_event->data;
  39
  40        switch (event) {
  41        case FB_EVENT_BLANK :
  42                if (*blank && n->old_status == UNBLANK) {
  43                        n->brightness = led->brightness;
  44                        led_set_brightness(led, LED_OFF);
  45                        n->old_status = BLANK;
  46                } else if (!*blank && n->old_status == BLANK) {
  47                        led_set_brightness(led, n->brightness);
  48                        n->old_status = UNBLANK;
  49                }
  50                break;
  51        }
  52
  53        return 0;
  54}
  55
  56static void bl_trig_activate(struct led_classdev *led)
  57{
  58        int ret;
  59
  60        struct bl_trig_notifier *n;
  61
  62        n = kzalloc(sizeof(struct bl_trig_notifier), GFP_KERNEL);
  63        led->trigger_data = n;
  64        if (!n) {
  65                dev_err(led->dev, "unable to allocate backlight trigger\n");
  66                return;
  67        }
  68
  69        n->led = led;
  70        n->brightness = led->brightness;
  71        n->old_status = UNBLANK;
  72        n->notifier.notifier_call = fb_notifier_callback;
  73
  74        ret = fb_register_client(&n->notifier);
  75        if (ret)
  76                dev_err(led->dev, "unable to register backlight trigger\n");
  77}
  78
  79static void bl_trig_deactivate(struct led_classdev *led)
  80{
  81        struct bl_trig_notifier *n =
  82                (struct bl_trig_notifier *) led->trigger_data;
  83
  84        if (n) {
  85                fb_unregister_client(&n->notifier);
  86                kfree(n);
  87        }
  88}
  89
  90static struct led_trigger bl_led_trigger = {
  91        .name           = "backlight",
  92        .activate       = bl_trig_activate,
  93        .deactivate     = bl_trig_deactivate
  94};
  95
  96static int __init bl_trig_init(void)
  97{
  98        return led_trigger_register(&bl_led_trigger);
  99}
 100
 101static void __exit bl_trig_exit(void)
 102{
 103        led_trigger_unregister(&bl_led_trigger);
 104}
 105
 106module_init(bl_trig_init);
 107module_exit(bl_trig_exit);
 108
 109MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 110MODULE_DESCRIPTION("Backlight emulation LED trigger");
 111MODULE_LICENSE("GPL v2");
 112