1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Backlight emulation LED trigger
4  *
5  * Copyright 2008 (C) Rodolfo Giometti <giometti@linux.it>
6  * Copyright 2008 (C) Eurotech S.p.A. <info@eurotech.it>
7  */
8 
9 #include <linux/module.h>
10 #include <linux/kernel.h>
11 #include <linux/slab.h>
12 #include <linux/init.h>
13 #include <linux/fb.h>
14 #include <linux/leds.h>
15 #include "../leds.h"
16 
17 #define BLANK		1
18 #define UNBLANK		0
19 
20 struct bl_trig_notifier {
21 	struct led_classdev *led;
22 	int brightness;
23 	int old_status;
24 	struct notifier_block notifier;
25 	unsigned invert;
26 };
27 
28 static int fb_notifier_callback(struct notifier_block *p,
29 				unsigned long event, void *data)
30 {
31 	struct bl_trig_notifier *n = container_of(p,
32 					struct bl_trig_notifier, notifier);
33 	struct led_classdev *led = n->led;
34 	struct fb_event *fb_event = data;
35 	int *blank;
36 	int new_status;
37 
38 	/* If we aren't interested in this event, skip it immediately ... */
39 	if (event != FB_EVENT_BLANK)
40 		return 0;
41 
42 	blank = fb_event->data;
43 	new_status = *blank ? BLANK : UNBLANK;
44 
45 	if (new_status == n->old_status)
46 		return 0;
47 
48 	if ((n->old_status == UNBLANK) ^ n->invert) {
49 		n->brightness = led->brightness;
50 		led_set_brightness_nosleep(led, LED_OFF);
51 	} else {
52 		led_set_brightness_nosleep(led, n->brightness);
53 	}
54 
55 	n->old_status = new_status;
56 
57 	return 0;
58 }
59 
60 static ssize_t bl_trig_invert_show(struct device *dev,
61 		struct device_attribute *attr, char *buf)
62 {
63 	struct bl_trig_notifier *n = led_trigger_get_drvdata(dev);
64 
65 	return sprintf(buf, "%u\n", n->invert);
66 }
67 
68 static ssize_t bl_trig_invert_store(struct device *dev,
69 		struct device_attribute *attr, const char *buf, size_t num)
70 {
71 	struct led_classdev *led = led_trigger_get_led(dev);
72 	struct bl_trig_notifier *n = led_trigger_get_drvdata(dev);
73 	unsigned long invert;
74 	int ret;
75 
76 	ret = kstrtoul(buf, 10, &invert);
77 	if (ret < 0)
78 		return ret;
79 
80 	if (invert > 1)
81 		return -EINVAL;
82 
83 	n->invert = invert;
84 
85 	/* After inverting, we need to update the LED. */
86 	if ((n->old_status == BLANK) ^ n->invert)
87 		led_set_brightness_nosleep(led, LED_OFF);
88 	else
89 		led_set_brightness_nosleep(led, n->brightness);
90 
91 	return num;
92 }
93 static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store);
94 
95 static struct attribute *bl_trig_attrs[] = {
96 	&dev_attr_inverted.attr,
97 	NULL,
98 };
99 ATTRIBUTE_GROUPS(bl_trig);
100 
101 static int bl_trig_activate(struct led_classdev *led)
102 {
103 	int ret;
104 
105 	struct bl_trig_notifier *n;
106 
107 	n = kzalloc(sizeof(struct bl_trig_notifier), GFP_KERNEL);
108 	if (!n)
109 		return -ENOMEM;
110 	led_set_trigger_data(led, n);
111 
112 	n->led = led;
113 	n->brightness = led->brightness;
114 	n->old_status = UNBLANK;
115 	n->notifier.notifier_call = fb_notifier_callback;
116 
117 	ret = fb_register_client(&n->notifier);
118 	if (ret)
119 		dev_err(led->dev, "unable to register backlight trigger\n");
120 
121 	return 0;
122 }
123 
124 static void bl_trig_deactivate(struct led_classdev *led)
125 {
126 	struct bl_trig_notifier *n = led_get_trigger_data(led);
127 
128 	fb_unregister_client(&n->notifier);
129 	kfree(n);
130 }
131 
132 static struct led_trigger bl_led_trigger = {
133 	.name		= "backlight",
134 	.activate	= bl_trig_activate,
135 	.deactivate	= bl_trig_deactivate,
136 	.groups		= bl_trig_groups,
137 };
138 module_led_trigger(bl_led_trigger);
139 
140 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
141 MODULE_DESCRIPTION("Backlight emulation LED trigger");
142 MODULE_LICENSE("GPL v2");
143