[PATCH] LED: add LED heartbeat trigger

Add an LED trigger acts like a heart beat.  This can be used as a
replacement of CONFIG_HEARTBEAT code exists in some arch's timer code.
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Acked-by: Richard Purdie <rpurdie@rpsys.net>
Cc: "Nish Aravamudan" <nish.aravamudan@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/leds/Kconfig

@@ -93,5 +93,14 @@ config LEDS_TRIGGER_IDE_DISK
 	  This allows LEDs to be controlled by IDE disk activity.
 	  If unsure, say Y.
 
+config LEDS_TRIGGER_HEARTBEAT
+	tristate "LED Heartbeat Trigger"
+	depends LEDS_TRIGGERS
+	help
+	  This allows LEDs to be controlled by a CPU load average.
+	  The flash frequency is a hyperbolic function of the 1-minute
+	  load average.
+	  If unsure, say Y.
+
 endmenu
 

drivers/leds/Makefile

@@ -16,3 +16,4 @@ obj-$(CONFIG_LEDS_AMS_DELTA)		+= leds-ams-delta.o
 # LED Triggers
 obj-$(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

drivers/leds/ledtrig-heartbeat.c

+/*
+ * LED Heartbeat Trigger
+ *
+ * Copyright (C) 2006 Atsushi Nemoto <anemo@mba.ocn.ne.jp>
+ *
+ * Based on Richard Purdie's ledtrig-timer.c and some arch's
+ * CONFIG_HEARTBEAT code.
+ *
+ * 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/timer.h>
+#include <linux/sched.h>
+#include <linux/leds.h>
+#include "leds.h"
+
+struct heartbeat_trig_data {
+	unsigned int phase;
+	unsigned int period;
+	struct timer_list timer;
+};
+
+static void led_heartbeat_function(unsigned long data)
+{
+	struct led_classdev *led_cdev = (struct led_classdev *) data;
+	struct heartbeat_trig_data *heartbeat_data = led_cdev->trigger_data;
+	unsigned long brightness = LED_OFF;
+	unsigned long delay = 0;
+
+	/* acts like an actual heart beat -- ie thump-thump-pause... */
+	switch (heartbeat_data->phase) {
+	case 0:
+		/*
+		 * The hyperbolic function below modifies the
+		 * heartbeat period length in dependency of the
+		 * current (1min) load. It goes through the points
+		 * f(0)=1260, f(1)=860, f(5)=510, f(inf)->300.
+		 */
+		heartbeat_data->period = 300 +
+			(6720 << FSHIFT) / (5 * avenrun[0] + (7 << FSHIFT));
+		heartbeat_data->period =
+			msecs_to_jiffies(heartbeat_data->period);
+		delay = msecs_to_jiffies(70);
+		heartbeat_data->phase++;
+		brightness = LED_FULL;
+		break;
+	case 1:
+		delay = heartbeat_data->period / 4 - msecs_to_jiffies(70);
+		heartbeat_data->phase++;
+		break;
+	case 2:
+		delay = msecs_to_jiffies(70);
+		heartbeat_data->phase++;
+		brightness = LED_FULL;
+		break;
+	default:
+		delay = heartbeat_data->period - heartbeat_data->period / 4 -
+			msecs_to_jiffies(70);
+		heartbeat_data->phase = 0;
+		break;
+	}
+
+	led_set_brightness(led_cdev, brightness);
+	mod_timer(&heartbeat_data->timer, jiffies + delay);
+}
+
+static void heartbeat_trig_activate(struct led_classdev *led_cdev)
+{
+	struct heartbeat_trig_data *heartbeat_data;
+
+	heartbeat_data = kzalloc(sizeof(*heartbeat_data), GFP_KERNEL);
+	if (!heartbeat_data)
+		return;
+
+	led_cdev->trigger_data = heartbeat_data;
+	setup_timer(&heartbeat_data->timer,
+		    led_heartbeat_function, (unsigned long) led_cdev);
+	heartbeat_data->phase = 0;
+	led_heartbeat_function(heartbeat_data->timer.data);
+}
+
+static void heartbeat_trig_deactivate(struct led_classdev *led_cdev)
+{
+	struct heartbeat_trig_data *heartbeat_data = led_cdev->trigger_data;
+
+	if (heartbeat_data) {
+		del_timer_sync(&heartbeat_data->timer);
+		kfree(heartbeat_data);
+	}
+}
+
+static struct led_trigger heartbeat_led_trigger = {
+	.name     = "heartbeat",
+	.activate = heartbeat_trig_activate,
+	.deactivate = heartbeat_trig_deactivate,
+};
+
+static int __init heartbeat_trig_init(void)
+{
+	return led_trigger_register(&heartbeat_led_trigger);
+}
+
+static void __exit heartbeat_trig_exit(void)
+{
+	led_trigger_unregister(&heartbeat_led_trigger);
+}
+
+module_init(heartbeat_trig_init);
+module_exit(heartbeat_trig_exit);
+
+MODULE_AUTHOR("Atsushi Nemoto <anemo@mba.ocn.ne.jp>");
+MODULE_DESCRIPTION("Heartbeat LED trigger");
+MODULE_LICENSE("GPL");