LXR linux/drivers/leds/ledtrig-backlight.c

   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/init.h>
  16#include <linux/fb.h>
  17#include <linux/leds.h>
  18#include "leds.h"
  19
  20#define BLANK           1
  21#define UNBLANK         0
  22
  23struct bl_trig_notifier {
  24        struct led_classdev *led;
  25        int brightness;
  26        int old_status;
  27        struct notifier_block notifier;
  28};
  29
  30static int fb_notifier_callback(struct notifier_block *p,
  31                                unsigned long event, void *data)
  32{
  33        struct bl_trig_notifier *n = container_of(p,
  34                                        struct bl_trig_notifier, notifier);
  35        struct led_classdev *led = n->led;
  36        struct fb_event *fb_event = data;
  37        int *blank = fb_event->data;
  38
  39        switch (event) {
  40        case FB_EVENT_BLANK :
  41                if (*blank && n->old_status == UNBLANK) {
  42                        n->brightness = led->brightness;
  43                        led_set_brightness(led, LED_OFF);
  44                        n->old_status = BLANK;
  45                } else if (!*blank && n->old_status == BLANK) {
  46                        led_set_brightness(led, n->brightness);
  47                        n->old_status = UNBLANK;
  48                }
  49                break;
  50        }
  51
  52        return 0;
  53}
  54
  55static void bl_trig_activate(struct led_classdev *led)
  56{
  57        int ret;
  58
  59        struct bl_trig_notifier *n;
  60
  61        n = kzalloc(sizeof(struct bl_trig_notifier), GFP_KERNEL);
  62        led->trigger_data = n;
  63        if (!n) {
  64                dev_err(led->dev, "unable to allocate backlight trigger\n");
  65                return;
  66        }
  67
  68        n->led = led;
  69        n->brightness = led->brightness;
  70        n->old_status = UNBLANK;
  71        n->notifier.notifier_call = fb_notifier_callback;
  72
  73        ret = fb_register_client(&n->notifier);
  74        if (ret)
  75                dev_err(led->dev, "unable to register backlight trigger\n");
  76}
  77
  78static void bl_trig_deactivate(struct led_classdev *led)
  79{
  80        struct bl_trig_notifier *n =
  81                (struct bl_trig_notifier *) led->trigger_data;
  82
  83        if (n) {
  84                fb_unregister_client(&n->notifier);
  85                kfree(n);
  86        }
  87}
  88
  89static struct led_trigger bl_led_trigger = {
  90        .name           = "backlight",
  91        .activate       = bl_trig_activate,
  92        .deactivate     = bl_trig_deactivate
  93};
  94
  95static int __init bl_trig_init(void)
  96{
  97        return led_trigger_register(&bl_led_trigger);
  98}
  99
 100static void __exit bl_trig_exit(void)
 101{
 102        led_trigger_unregister(&bl_led_trigger);
 103}
 104
 105module_init(bl_trig_init);
 106module_exit(bl_trig_exit);
 107
 108MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 109MODULE_DESCRIPTION("Backlight emulation LED trigger");
 110MODULE_LICENSE("GPL v2");
 111