drivers/leds/trigger/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;
  40         int new_status;
  41
  42         /* If we aren't interested in this event, skip it immediately ... */
  43         if (event != FB_EVENT_BLANK)
  44                 return 0;
  45
  46         blank = fb_event->data;
  47         new_status = *blank ? BLANK : UNBLANK;
  48
  49         if (new_status == n->old_status)
  50                 return 0;
  51
  52         if ((n->old_status == UNBLANK) ^ n->invert) {
  53                 n->brightness = led->brightness;
  54                 __led_set_brightness(led, LED_OFF);
  55         } else {
  56                 __led_set_brightness(led, n->brightness);
  57         }
  58
  59         n->old_status = new_status;
  60
  61         return 0;
  62 }
  63
  64 static ssize_t bl_trig_invert_show(struct device *dev,
  65                 struct device_attribute *attr, char *buf)
  66 {
  67         struct led_classdev *led = dev_get_drvdata(dev);
  68         struct bl_trig_notifier *n = led->trigger_data;
  69
  70         return sprintf(buf, "%u\n", n->invert);
  71 }
  72
  73 static ssize_t bl_trig_invert_store(struct device *dev,
  74                 struct device_attribute *attr, const char *buf, size_t num)
  75 {
  76         struct led_classdev *led = dev_get_drvdata(dev);
  77         struct bl_trig_notifier *n = led->trigger_data;
  78         unsigned long invert;
  79         int ret;
  80
  81         ret = kstrtoul(buf, 10, &invert);
  82         if (ret < 0)
  83                 return ret;
  84
  85         if (invert > 1)
  86                 return -EINVAL;
  87
  88         n->invert = invert;
  89
  90         /* After inverting, we need to update the LED. */
  91         if ((n->old_status == BLANK) ^ n->invert)
  92                 __led_set_brightness(led, LED_OFF);
  93         else
  94                 __led_set_brightness(led, n->brightness);
  95
  96         return num;
  97 }
  98 static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store);
  99
 100 static void bl_trig_activate(struct led_classdev *led)
 101 {
 102         int ret;
 103
 104         struct bl_trig_notifier *n;
 105
 106         n = kzalloc(sizeof(struct bl_trig_notifier), GFP_KERNEL);
 107         led->trigger_data = n;
 108         if (!n) {
 109                 dev_err(led->dev, "unable to allocate backlight trigger\n");
 110                 return;
 111         }
 112
 113         ret = device_create_file(led->dev, &dev_attr_inverted);
 114         if (ret)
 115                 goto err_invert;
 116
 117         n->led = led;
 118         n->brightness = led->brightness;
 119         n->old_status = UNBLANK;
 120         n->notifier.notifier_call = fb_notifier_callback;
 121
 122         ret = fb_register_client(&n->notifier);
 123         if (ret)
 124                 dev_err(led->dev, "unable to register backlight trigger\n");
 125         led->activated = true;
 126
 127         return;
 128
 129 err_invert:
 130         led->trigger_data = NULL;
 131         kfree(n);
 132 }
 133
 134 static void bl_trig_deactivate(struct led_classdev *led)
 135 {
 136         struct bl_trig_notifier *n =
 137                 (struct bl_trig_notifier *) led->trigger_data;
 138
 139         if (led->activated) {
 140                 device_remove_file(led->dev, &dev_attr_inverted);
 141                 fb_unregister_client(&n->notifier);
 142                 kfree(n);
 143                 led->activated = false;
 144         }
 145 }
 146
 147 static struct led_trigger bl_led_trigger = {
 148         .name           = "backlight",
 149         .activate       = bl_trig_activate,
 150         .deactivate     = bl_trig_deactivate
 151 };
 152
 153 static int __init bl_trig_init(void)
 154 {
 155         return led_trigger_register(&bl_led_trigger);
 156 }
 157
 158 static void __exit bl_trig_exit(void)
 159 {
 160         led_trigger_unregister(&bl_led_trigger);
 161 }
 162
 163 module_init(bl_trig_init);
 164 module_exit(bl_trig_exit);
 165
 166 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 167 MODULE_DESCRIPTION("Backlight emulation LED trigger");
 168 MODULE_LICENSE("GPL v2");