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