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/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
  24 struct bl_trig_notifier {
  25         struct led_classdev *led;
  26         int brightness;
  27         int old_status;
  28         struct notifier_block notifier;
  29 };
  30
  31 static 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
  56 static 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
  79 static 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
  90 static struct led_trigger bl_led_trigger = {
  91         .name           = "backlight",
  92         .activate       = bl_trig_activate,
  93         .deactivate     = bl_trig_deactivate
  94 };
  95
  96 static int __init bl_trig_init(void)
  97 {
  98         return led_trigger_register(&bl_led_trigger);
  99 }
 100
 101 static void __exit bl_trig_exit(void)
 102 {
 103         led_trigger_unregister(&bl_led_trigger);
 104 }
 105
 106 module_init(bl_trig_init);
 107 module_exit(bl_trig_exit);
 108
 109 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 110 MODULE_DESCRIPTION("Backlight emulation LED trigger");
 111 MODULE_LICENSE("GPL v2");