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
24struct 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
32static 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
64static 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
73static 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}
98static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store);
99
100static 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
129err_invert:
130	led->trigger_data = NULL;
131	kfree(n);
132}
133
134static 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
147static struct led_trigger bl_led_trigger = {
148	.name		= "backlight",
149	.activate	= bl_trig_activate,
150	.deactivate	= bl_trig_deactivate
151};
152
153static int __init bl_trig_init(void)
154{
155	return led_trigger_register(&bl_led_trigger);
156}
157
158static void __exit bl_trig_exit(void)
159{
160	led_trigger_unregister(&bl_led_trigger);
161}
162
163module_init(bl_trig_init);
164module_exit(bl_trig_exit);
165
166MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
167MODULE_DESCRIPTION("Backlight emulation LED trigger");
168MODULE_LICENSE("GPL v2");
169