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         unsigned invert;
  30 };
  31
  32 static int fb_notifier_callback(struct notifier_block *p,
  33                                 unsigned long event, void *data)
  34 {
  35         struct bl_trig_notifier *n = container_of(p,
  36                                         struct bl_trig_notifier, notifier);
  37         struct led_classdev *led = n->led;
  38         struct fb_event *fb_event = data;
  39         int *blank = fb_event->data;
  40         int new_status = *blank ? BLANK : UNBLANK;
  41
  42         switch (event) {
  43         case FB_EVENT_BLANK:
  44                 if (new_status == n->old_status)
  45                         break;
  46
  47                 if ((n->old_status == UNBLANK) ^ n->invert) {
  48                         n->brightness = led->brightness;
  49                         __led_set_brightness(led, LED_OFF);
  50                 } else {
  51                         __led_set_brightness(led, n->brightness);
  52                 }
  53
  54                 n->old_status = new_status;
  55
  56                 break;
  57         }
  58
  59         return 0;
  60 }
  61
  62 static ssize_t bl_trig_invert_show(struct device *dev,
  63                 struct device_attribute *attr, char *buf)
  64 {
  65         struct led_classdev *led = dev_get_drvdata(dev);
  66         struct bl_trig_notifier *n = led->trigger_data;
  67
  68         return sprintf(buf, "%u\n", n->invert);
  69 }
  70
  71 static ssize_t bl_trig_invert_store(struct device *dev,
  72                 struct device_attribute *attr, const char *buf, size_t num)
  73 {
  74         struct led_classdev *led = dev_get_drvdata(dev);
  75         struct bl_trig_notifier *n = led->trigger_data;
  76         unsigned long invert;
  77         int ret;
  78
  79         ret = kstrtoul(buf, 10, &invert);
  80         if (ret < 0)
  81                 return ret;
  82
  83         if (invert > 1)
  84                 return -EINVAL;
  85
  86         n->invert = invert;
  87
  88         /* After inverting, we need to update the LED. */
  89         if ((n->old_status == BLANK) ^ n->invert)
  90                 __led_set_brightness(led, LED_OFF);
  91         else
  92                 __led_set_brightness(led, n->brightness);
  93
  94         return num;
  95 }
  96 static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store);
  97
  98 static void bl_trig_activate(struct led_classdev *led)
  99 {
 100         int ret;
 101
 102         struct bl_trig_notifier *n;
 103
 104         n = kzalloc(sizeof(struct bl_trig_notifier), GFP_KERNEL);
 105         led->trigger_data = n;
 106         if (!n) {
 107                 dev_err(led->dev, "unable to allocate backlight trigger\n");
 108                 return;
 109         }
 110
 111         ret = device_create_file(led->dev, &dev_attr_inverted);
 112         if (ret)
 113                 goto err_invert;
 114
 115         n->led = led;
 116         n->brightness = led->brightness;
 117         n->old_status = UNBLANK;
 118         n->notifier.notifier_call = fb_notifier_callback;
 119
 120         ret = fb_register_client(&n->notifier);
 121         if (ret)
 122                 dev_err(led->dev, "unable to register backlight trigger\n");
 123         led->activated = true;
 124
 125         return;
 126
 127 err_invert:
 128         led->trigger_data = NULL;
 129         kfree(n);
 130 }
 131
 132 static void bl_trig_deactivate(struct led_classdev *led)
 133 {
 134         struct bl_trig_notifier *n =
 135                 (struct bl_trig_notifier *) led->trigger_data;
 136
 137         if (led->activated) {
 138                 device_remove_file(led->dev, &dev_attr_inverted);
 139                 fb_unregister_client(&n->notifier);
 140                 kfree(n);
 141                 led->activated = false;
 142         }
 143 }
 144
 145 static struct led_trigger bl_led_trigger = {
 146         .name           = "backlight",
 147         .activate       = bl_trig_activate,
 148         .deactivate     = bl_trig_deactivate
 149 };
 150
 151 static int __init bl_trig_init(void)
 152 {
 153         return led_trigger_register(&bl_led_trigger);
 154 }
 155
 156 static void __exit bl_trig_exit(void)
 157 {
 158         led_trigger_unregister(&bl_led_trigger);
 159 }
 160
 161 module_init(bl_trig_init);
 162 module_exit(bl_trig_exit);
 163
 164 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 165 MODULE_DESCRIPTION("Backlight emulation LED trigger");
 166 MODULE_LICENSE("GPL v2");