LXR linux/drivers/leds/trigger/ledtrig-backlight.c

   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
  24struct 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
  32static 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(led, LED_OFF);
  55        } else {
  56                __led_set_brightness(led, n->brightness);
  57        }
  58
  59        n->old_status = new_status;
  60
  61        return 0;
  62}
  63
  64static 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
  73static 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(led, LED_OFF);
  93        else
  94                __led_set_brightness(led, n->brightness);
  95
  96        return num;
  97}
  98static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store);
  99
 100static 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
 129err_invert:
 130        led->trigger_data = NULL;
 131        kfree(n);
 132}
 133
 134static 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
 147static struct led_trigger bl_led_trigger = {
 148        .name           = "backlight",
 149        .activate       = bl_trig_activate,
 150        .deactivate     = bl_trig_deactivate
 151};
 152
 153static int __init bl_trig_init(void)
 154{
 155        return led_trigger_register(&bl_led_trigger);
 156}
 157
 158static void __exit bl_trig_exit(void)
 159{
 160        led_trigger_unregister(&bl_led_trigger);
 161}
 162
 163module_init(bl_trig_init);
 164module_exit(bl_trig_exit);
 165
 166MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 167MODULE_DESCRIPTION("Backlight emulation LED trigger");
 168MODULE_LICENSE("GPL v2");
 169