ledtrig-backlight.c

  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/leds.h>
 14#include "../leds.h"
 15
 16#define BLANK		1
 17#define UNBLANK		0
 18
 19struct bl_trig_notifier {
 20	struct led_classdev *led;
 21	int brightness;
 22	int old_status;
 23	unsigned invert;
 24
 25	struct list_head entry;
 26};
 27
 28static DEFINE_MUTEX(ledtrig_backlight_list_mutex);
 29static LIST_HEAD(ledtrig_backlight_list);
 30
 31static void ledtrig_backlight_notify_blank(struct bl_trig_notifier *n, int new_status)
 32{
 33	struct led_classdev *led = n->led;
 34
 35	if (new_status == n->old_status)
 36		return;
 37
 38	if ((n->old_status == UNBLANK) ^ n->invert) {
 39		n->brightness = led->brightness;
 40		led_set_brightness_nosleep(led, LED_OFF);
 41	} else {
 42		led_set_brightness_nosleep(led, n->brightness);
 43	}
 44
 45	n->old_status = new_status;
 46}
 47
 48void ledtrig_backlight_blank(bool blank)
 49{
 50	struct bl_trig_notifier *n;
 51	int new_status = blank ? BLANK : UNBLANK;
 52
 53	guard(mutex)(&ledtrig_backlight_list_mutex);
 54
 55	list_for_each_entry(n, &ledtrig_backlight_list, entry)
 56		ledtrig_backlight_notify_blank(n, new_status);
 57}
 58EXPORT_SYMBOL(ledtrig_backlight_blank);
 59
 60static 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
 68static 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}
 93static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store);
 94
 95static struct attribute *bl_trig_attrs[] = {
 96	&dev_attr_inverted.attr,
 97	NULL,
 98};
 99ATTRIBUTE_GROUPS(bl_trig);
100
101static int bl_trig_activate(struct led_classdev *led)
102{
103	struct bl_trig_notifier *n;
104
105	n = kzalloc(sizeof(struct bl_trig_notifier), GFP_KERNEL);
106	if (!n)
107		return -ENOMEM;
108	led_set_trigger_data(led, n);
109
110	n->led = led;
111	n->brightness = led->brightness;
112	n->old_status = UNBLANK;
113
114	guard(mutex)(&ledtrig_backlight_list_mutex);
115	list_add(&n->entry, &ledtrig_backlight_list);
116
117	return 0;
118}
119
120static void bl_trig_deactivate(struct led_classdev *led)
121{
122	struct bl_trig_notifier *n = led_get_trigger_data(led);
123
124	guard(mutex)(&ledtrig_backlight_list_mutex);
125	list_del(&n->entry);
126
127	kfree(n);
128}
129
130static struct led_trigger bl_led_trigger = {
131	.name		= "backlight",
132	.activate	= bl_trig_activate,
133	.deactivate	= bl_trig_deactivate,
134	.groups		= bl_trig_groups,
135};
136module_led_trigger(bl_led_trigger);
137
138MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
139MODULE_DESCRIPTION("Backlight emulation LED trigger");
140MODULE_LICENSE("GPL v2");