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"); 143