Attempting to consolidate the ARM LED code, this removes the
custom RealView LED trigger code to turn LEDs on and off in
response to CPU activity and replace it with a standard trigger.

(bryan.wu at canonical.com:
It introduces several syscore stubs into this trigger.
It also provides ledtrig_cpu trigger event stub in <linux/leds.h>.
Although it was inspired by ARM work, it can be used in other arch.)

Cc: Richard Purdie <redacted>
Signed-off-by: Linus Walleij <redacted>
Signed-off-by: Bryan Wu <redacted>
Reviewed-by: Jamie Iles <redacted>
Tested-by: Jochen Friedrich <jochen@scram.de>
---
 drivers/leds/Kconfig       |   10 +++
 drivers/leds/Makefile      |    1 +
 drivers/leds/ledtrig-cpu.c |  163 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/leds.h       |   16 +++++
 4 files changed, 190 insertions(+)
 create mode 100644 drivers/leds/ledtrig-cpu.c

diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 5f12659..dbf8a4c 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig

@@ -465,6 +465,16 @@ config LEDS_TRIGGER_BACKLIGHT
 
 	  If unsure, say N.
 
+config LEDS_TRIGGER_CPU
+	tristate "LED CPU Trigger"
+	depends on LEDS_TRIGGERS
+	help
+	  This allows LEDs to be controlled by active CPUs. This shows
+	  the active CPUs across an array of LEDs so you can see which
+	  CPUs are active on the system at any given moment.
+
+	  If unsure, say N.
+
 config LEDS_TRIGGER_GPIO
 	tristate "LED GPIO Trigger"
 	depends on LEDS_TRIGGERS

diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
index 9475bbb..ea1efb2 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile

@@ -56,4 +56,5 @@ 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_GPIO)		+= ledtrig-gpio.o
+obj-$(CONFIG_LEDS_TRIGGER_CPU)		+= ledtrig-cpu.o
 obj-$(CONFIG_LEDS_TRIGGER_DEFAULT_ON)	+= ledtrig-default-on.o

diff --git a/drivers/leds/ledtrig-cpu.c b/drivers/leds/ledtrig-cpu.c
new file mode 100644
index 0000000..b312056
--- /dev/null
+++ b/drivers/leds/ledtrig-cpu.c

@@ -0,0 +1,163 @@
+/*
+ * ledtrig-cpu.c - LED trigger based on CPU activity
+ *
+ * This LED trigger will be registered for each possible CPU and named as
+ * cpu0, cpu1, cpu2, cpu3, etc.
+ *
+ * It can be bound to any LED just like other triggers using either a
+ * board file or via sysfs interface.
+ *
+ * An API named ledtrig_cpu is exported for any user, who want to add CPU
+ * activity indication in their code
+ *
+ * Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
+ * Copyright 2011 - 2012 Bryan Wu <bryan.wu@canonical.com>
+ *
+ * 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/slab.h>
+#include <linux/percpu.h>
+#include <linux/syscore_ops.h>
+#include <linux/rwsem.h>
+#include "leds.h"
+
+#define MAX_NAME_LEN	8
+
+struct led_trigger_cpu {
+	char name[MAX_NAME_LEN];
+	struct led_trigger *_trig;
+	struct mutex lock;
+	int lock_is_inited;
+};
+
+static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);
+
+/**
+ * ledtrig_cpu - emit a CPU event as a trigger
+ * @evt: CPU event to be emitted
+ *
+ * Emit a CPU event on a CPU core, which will trigger a
+ * binded LED to turn on or turn off.
+ */
+void ledtrig_cpu(enum cpu_led_event ledevt)
+{
+	struct led_trigger_cpu *trig = &__get_cpu_var(cpu_trig);
+
+	/* mutex lock should be initialized before calling mutex_call() */
+	if (!trig->lock_is_inited)
+		return;