1 // SPDX-License-Identifier: GPL-2.0-only
3 * Backlight emulation LED trigger
5 * Copyright 2008 (C) Rodolfo Giometti <giometti@linux.it>
6 * Copyright 2008 (C) Eurotech S.p.A. <info@eurotech.it>
9 #include <linux/module.h>
10 #include <linux/kernel.h>
11 #include <linux/slab.h>
12 #include <linux/init.h>
14 #include <linux/leds.h>
20 struct bl_trig_notifier {
21 struct led_classdev *led;
24 struct notifier_block notifier;
28 static int fb_notifier_callback(struct notifier_block *p,
29 unsigned long event, void *data)
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;
38 /* If we aren't interested in this event, skip it immediately ... */
39 if (event != FB_EVENT_BLANK)
42 blank = fb_event->data;
43 new_status = *blank ? BLANK : UNBLANK;
45 if (new_status == n->old_status)
48 if ((n->old_status == UNBLANK) ^ n->invert) {
49 n->brightness = led->brightness;
50 led_set_brightness_nosleep(led, LED_OFF);
52 led_set_brightness_nosleep(led, n->brightness);
55 n->old_status = new_status;
60 static ssize_t bl_trig_invert_show(struct device *dev,
61 struct device_attribute *attr, char *buf)
63 struct bl_trig_notifier *n = led_trigger_get_drvdata(dev);
65 return sprintf(buf, "%u\n", n->invert);
68 static ssize_t bl_trig_invert_store(struct device *dev,
69 struct device_attribute *attr, const char *buf, size_t num)
71 struct led_classdev *led = led_trigger_get_led(dev);
72 struct bl_trig_notifier *n = led_trigger_get_drvdata(dev);
76 ret = kstrtoul(buf, 10, &invert);
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);
89 led_set_brightness_nosleep(led, n->brightness);
93 static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store);
95 static struct attribute *bl_trig_attrs[] = {
96 &dev_attr_inverted.attr,
99 ATTRIBUTE_GROUPS(bl_trig);
101 static int bl_trig_activate(struct led_classdev *led)
105 struct bl_trig_notifier *n;
107 n = kzalloc(sizeof(struct bl_trig_notifier), GFP_KERNEL);
110 led_set_trigger_data(led, n);
113 n->brightness = led->brightness;
114 n->old_status = UNBLANK;
115 n->notifier.notifier_call = fb_notifier_callback;
117 ret = fb_register_client(&n->notifier);
119 dev_err(led->dev, "unable to register backlight trigger\n");
124 static void bl_trig_deactivate(struct led_classdev *led)
126 struct bl_trig_notifier *n = led_get_trigger_data(led);
128 fb_unregister_client(&n->notifier);
132 static struct led_trigger bl_led_trigger = {
134 .activate = bl_trig_activate,
135 .deactivate = bl_trig_deactivate,
136 .groups = bl_trig_groups,
138 module_led_trigger(bl_led_trigger);
140 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
141 MODULE_DESCRIPTION("Backlight emulation LED trigger");
142 MODULE_LICENSE("GPL v2");