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
fb_notifier_callback(struct notifier_block * p,unsigned long event,void * data)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
bl_trig_invert_show(struct device * dev,struct device_attribute * attr,char * buf)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
bl_trig_invert_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t num)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
bl_trig_activate(struct led_classdev * led)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
bl_trig_deactivate(struct led_classdev * led)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