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");
147