LXR linux/drivers/leds/trigger/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/fb.h>
  14#include <linux/leds.h>
  15#include "../leds.h"
  16
  17#define BLANK           1
  18#define UNBLANK         0
  19
  20struct 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
  28static 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
  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        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
 124static 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
 132static 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};
 138module_led_trigger(bl_led_trigger);
 139
 140MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 141MODULE_DESCRIPTION("Backlight emulation LED trigger");
 142MODULE_LICENSE("GPL v2");
 143