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 24 struct 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 32 static 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_async(led, LED_OFF); 55 } else { 56 led_set_brightness_async(led, n->brightness); 57 } 58 59 n->old_status = new_status; 60 61 return 0; 62 } 63 64 static 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 73 static 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_async(led, LED_OFF); 93 else 94 led_set_brightness_async(led, n->brightness); 95 96 return num; 97 } 98 static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store); 99 100 static 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; 128 129 err_invert: 130 led->trigger_data = NULL; 131 kfree(n); 132 } 133 134 static 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 } 146 147 static struct led_trigger bl_led_trigger = { 148 .name = "backlight", 149 .activate = bl_trig_activate, 150 .deactivate = bl_trig_deactivate 151 }; 152 153 static int __init bl_trig_init(void) 154 { 155 return led_trigger_register(&bl_led_trigger); 156 } 157 158 static void __exit bl_trig_exit(void) 159 { 160 led_trigger_unregister(&bl_led_trigger); 161 } 162 163 module_init(bl_trig_init); 164 module_exit(bl_trig_exit); 165 166 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>"); 167 MODULE_DESCRIPTION("Backlight emulation LED trigger"); 168 MODULE_LICENSE("GPL v2"); 169