leds: Add backlight LED trigger

This allows LEDs to be controlled as a backlight device where
they turn off and on when the display is blanked and unblanked.
This is useful where you need various key backlight LEDs to
dim at the same time as the backlight.
Signed-off-by: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

drivers/leds/Kconfig

@@ -200,6 +200,15 @@ config LEDS_TRIGGER_HEARTBEAT
 	  load average.
 	  If unsure, say Y.
 
+config LEDS_TRIGGER_BACKLIGHT
+	tristate "LED backlight Trigger"
+	depends on LEDS_TRIGGERS
+	help
+	  This allows LEDs to be controlled as a backlight device: they
+	  turn off and on when the display is blanked and unblanked.
+
+	  If unsure, say N.
+
 config LEDS_TRIGGER_DEFAULT_ON
 	tristate "LED Default ON Trigger"
 	depends on LEDS_TRIGGERS

drivers/leds/Makefile

@@ -28,4 +28,5 @@ obj-$(CONFIG_LEDS_DA903X)		+= leds-da903x.o
 obj-$(CONFIG_LEDS_TRIGGER_TIMER)	+= ledtrig-timer.o
 obj-$(CONFIG_LEDS_TRIGGER_IDE_DISK)	+= ledtrig-ide-disk.o
 obj-$(CONFIG_LEDS_TRIGGER_HEARTBEAT)	+= ledtrig-heartbeat.o
+obj-$(CONFIG_LEDS_TRIGGER_BACKLIGHT)	+= ledtrig-backlight.o
 obj-$(CONFIG_LEDS_TRIGGER_DEFAULT_ON)	+= ledtrig-default-on.o

drivers/leds/ledtrig-backlight.c

+/*
+ * Backlight emulation LED trigger
+ *
+ * Copyright 2008 (C) Rodolfo Giometti <giometti@linux.it>
+ * Copyright 2008 (C) Eurotech S.p.A. <info@eurotech.it>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/fb.h>
+#include <linux/leds.h>
+#include "leds.h"
+
+#define BLANK		1
+#define UNBLANK		0
+
+struct bl_trig_notifier {
+	struct led_classdev *led;
+	int brightness;
+	int old_status;
+	struct notifier_block notifier;
+};
+
+static int fb_notifier_callback(struct notifier_block *p,
+				unsigned long event, void *data)
+{
+	struct bl_trig_notifier *n = container_of(p,
+					struct bl_trig_notifier, notifier);
+	struct led_classdev *led = n->led;
+	struct fb_event *fb_event = data;
+	int *blank = fb_event->data;
+
+	switch (event) {
+	case FB_EVENT_BLANK :
+		if (*blank && n->old_status == UNBLANK) {
+			n->brightness = led->brightness;
+			led_set_brightness(led, LED_OFF);
+			n->old_status = BLANK;
+		} else if (!*blank && n->old_status == BLANK) {
+			led_set_brightness(led, n->brightness);
+			n->old_status = UNBLANK;
+		}
+		break;
+	}
+
+	return 0;
+}
+
+static void bl_trig_activate(struct led_classdev *led)
+{
+	int ret;
+
+	struct bl_trig_notifier *n;
+
+	n = kzalloc(sizeof(struct bl_trig_notifier), GFP_KERNEL);
+	led->trigger_data = n;
+	if (!n) {
+		dev_err(led->dev, "unable to allocate backlight trigger\n");
+		return;
+	}
+
+	n->led = led;
+	n->brightness = led->brightness;
+	n->old_status = UNBLANK;
+	n->notifier.notifier_call = fb_notifier_callback;
+
+	ret = fb_register_client(&n->notifier);
+	if (ret)
+		dev_err(led->dev, "unable to register backlight trigger\n");
+}
+
+static void bl_trig_deactivate(struct led_classdev *led)
+{
+	struct bl_trig_notifier *n =
+		(struct bl_trig_notifier *) led->trigger_data;
+
+	if (n) {
+		fb_unregister_client(&n->notifier);
+		kfree(n);
+	}
+}
+
+static struct led_trigger bl_led_trigger = {
+	.name		= "backlight",
+	.activate	= bl_trig_activate,
+	.deactivate	= bl_trig_deactivate
+};
+
+static int __init bl_trig_init(void)
+{
+	return led_trigger_register(&bl_led_trigger);
+}
+
+static void __exit bl_trig_exit(void)
+{
+	led_trigger_unregister(&bl_led_trigger);
+}
+
+module_init(bl_trig_init);
+module_exit(bl_trig_exit);
+
+MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
+MODULE_DESCRIPTION("Backlight emulation LED trigger");
+MODULE_LICENSE("GPL v2");