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_nosleep(led, LED_OFF);
  55         } else {
  56                 led_set_brightness_nosleep(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 bl_trig_notifier *n = led_trigger_get_drvdata(dev);
  68
  69         return sprintf(buf, "%u\n", n->invert);
  70 }
  71
  72 static ssize_t bl_trig_invert_store(struct device *dev,
  73                 struct device_attribute *attr, const char *buf, size_t num)
  74 {
  75         struct led_classdev *led = led_trigger_get_led(dev);
  76         struct bl_trig_notifier *n = led_trigger_get_drvdata(dev);
  77         unsigned long invert;
  78         int ret;
  79
  80         ret = kstrtoul(buf, 10, &invert);
  81         if (ret < 0)
  82                 return ret;
  83
  84         if (invert > 1)
  85                 return -EINVAL;
  86
  87         n->invert = invert;
  88
  89         /* After inverting, we need to update the LED. */
  90         if ((n->old_status == BLANK) ^ n->invert)
  91                 led_set_brightness_nosleep(led, LED_OFF);
  92         else
  93                 led_set_brightness_nosleep(led, n->brightness);
  94
  95         return num;
  96 }
  97 static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store);
  98
  99 static struct attribute *bl_trig_attrs[] = {
 100         &dev_attr_inverted.attr,
 101         NULL,
 102 };
 103 ATTRIBUTE_GROUPS(bl_trig);
 104
 105 static int bl_trig_activate(struct led_classdev *led)
 106 {
 107         int ret;
 108
 109         struct bl_trig_notifier *n;
 110
 111         n = kzalloc(sizeof(struct bl_trig_notifier), GFP_KERNEL);
 112         if (!n)
 113                 return -ENOMEM;
 114         led_set_trigger_data(led, n);
 115
 116         n->led = led;
 117         n->brightness = led->brightness;
 118         n->old_status = UNBLANK;
 119         n->notifier.notifier_call = fb_notifier_callback;
 120
 121         ret = fb_register_client(&n->notifier);
 122         if (ret)
 123                 dev_err(led->dev, "unable to register backlight trigger\n");
 124
 125         return 0;
 126 }
 127
 128 static void bl_trig_deactivate(struct led_classdev *led)
 129 {
 130         struct bl_trig_notifier *n = led_get_trigger_data(led);
 131
 132         fb_unregister_client(&n->notifier);
 133         kfree(n);
 134 }
 135
 136 static struct led_trigger bl_led_trigger = {
 137         .name           = "backlight",
 138         .activate       = bl_trig_activate,
 139         .deactivate     = bl_trig_deactivate,
 140         .groups         = bl_trig_groups,
 141 };
 142 module_led_trigger(bl_led_trigger);
 143
 144 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 145 MODULE_DESCRIPTION("Backlight emulation LED trigger");
 146 MODULE_LICENSE("GPL v2");