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
fb_notifier_callback(struct notifier_block * p,unsigned long event,void * data)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
bl_trig_invert_show(struct device * dev,struct device_attribute * attr,char * buf)64 static 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
bl_trig_invert_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t num)73 static 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_nosleep(led, LED_OFF);
93 else
94 led_set_brightness_nosleep(led, n->brightness);
95
96 return num;
97 }
98 static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store);
99
bl_trig_activate(struct led_classdev * led)100 static 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
129 err_invert:
130 led->trigger_data = NULL;
131 kfree(n);
132 }
133
bl_trig_deactivate(struct led_classdev * led)134 static 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
147 static struct led_trigger bl_led_trigger = {
148 .name = "backlight",
149 .activate = bl_trig_activate,
150 .deactivate = bl_trig_deactivate
151 };
152
bl_trig_init(void)153 static int __init bl_trig_init(void)
154 {
155 return led_trigger_register(&bl_led_trigger);
156 }
157
bl_trig_exit(void)158 static void __exit bl_trig_exit(void)
159 {
160 led_trigger_unregister(&bl_led_trigger);
161 }
162
163 module_init(bl_trig_init);
164 module_exit(bl_trig_exit);
165
166 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
167 MODULE_DESCRIPTION("Backlight emulation LED trigger");
168 MODULE_LICENSE("GPL v2");
169