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");
167