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 = fb_event->data; 40 int new_status = *blank ? BLANK : UNBLANK; 41 42 switch (event) { 43 case FB_EVENT_BLANK: 44 if (new_status == n->old_status) 45 break; 46 47 if ((n->old_status == UNBLANK) ^ n->invert) { 48 n->brightness = led->brightness; 49 __led_set_brightness(led, LED_OFF); 50 } else { 51 __led_set_brightness(led, n->brightness); 52 } 53 54 n->old_status = new_status; 55 56 break; 57 } 58 59 return 0; 60 } 61 62 static ssize_t bl_trig_invert_show(struct device *dev, 63 struct device_attribute *attr, char *buf) 64 { 65 struct led_classdev *led = dev_get_drvdata(dev); 66 struct bl_trig_notifier *n = led->trigger_data; 67 68 return sprintf(buf, "%u\n", n->invert); 69 } 70 71 static ssize_t bl_trig_invert_store(struct device *dev, 72 struct device_attribute *attr, const char *buf, size_t num) 73 { 74 struct led_classdev *led = dev_get_drvdata(dev); 75 struct bl_trig_notifier *n = led->trigger_data; 76 unsigned long invert; 77 int ret; 78 79 ret = kstrtoul(buf, 10, &invert); 80 if (ret < 0) 81 return ret; 82 83 if (invert > 1) 84 return -EINVAL; 85 86 n->invert = invert; 87 88 /* After inverting, we need to update the LED. */ 89 if ((n->old_status == BLANK) ^ n->invert) 90 __led_set_brightness(led, LED_OFF); 91 else 92 __led_set_brightness(led, n->brightness); 93 94 return num; 95 } 96 static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store); 97 98 static void bl_trig_activate(struct led_classdev *led) 99 { 100 int ret; 101 102 struct bl_trig_notifier *n; 103 104 n = kzalloc(sizeof(struct bl_trig_notifier), GFP_KERNEL); 105 led->trigger_data = n; 106 if (!n) { 107 dev_err(led->dev, "unable to allocate backlight trigger\n"); 108 return; 109 } 110 111 ret = device_create_file(led->dev, &dev_attr_inverted); 112 if (ret) 113 goto err_invert; 114 115 n->led = led; 116 n->brightness = led->brightness; 117 n->old_status = UNBLANK; 118 n->notifier.notifier_call = fb_notifier_callback; 119 120 ret = fb_register_client(&n->notifier); 121 if (ret) 122 dev_err(led->dev, "unable to register backlight trigger\n"); 123 led->activated = true; 124 125 return; 126 127 err_invert: 128 led->trigger_data = NULL; 129 kfree(n); 130 } 131 132 static void bl_trig_deactivate(struct led_classdev *led) 133 { 134 struct bl_trig_notifier *n = 135 (struct bl_trig_notifier *) led->trigger_data; 136 137 if (led->activated) { 138 device_remove_file(led->dev, &dev_attr_inverted); 139 fb_unregister_client(&n->notifier); 140 kfree(n); 141 led->activated = false; 142 } 143 } 144 145 static struct led_trigger bl_led_trigger = { 146 .name = "backlight", 147 .activate = bl_trig_activate, 148 .deactivate = bl_trig_deactivate 149 }; 150 151 static int __init bl_trig_init(void) 152 { 153 return led_trigger_register(&bl_led_trigger); 154 } 155 156 static void __exit bl_trig_exit(void) 157 { 158 led_trigger_unregister(&bl_led_trigger); 159 } 160 161 module_init(bl_trig_init); 162 module_exit(bl_trig_exit); 163 164 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>"); 165 MODULE_DESCRIPTION("Backlight emulation LED trigger"); 166 MODULE_LICENSE("GPL v2"); 167