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_async(led, LED_OFF);
55 	} else {
56 		led_set_brightness_async(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_async(led, LED_OFF);
93 	else
94 		led_set_brightness_async(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");
169