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
  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
  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
  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
  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
 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
 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");