diff mbox

[01/17] leds: create a trigger for CPU activity

Message ID 1309955687-19365-2-git-send-email-bryan.wu@canonical.com (mailing list archive)
State New, archived
Headers show

Commit Message

Bryan Wu July 6, 2011, 12:34 p.m. UTC
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@canonical.com:
It moves arch/arm/kernel/leds.c 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 <rpurdie@rpsys.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
---
 drivers/leds/Kconfig       |   10 +++
 drivers/leds/Makefile      |    1 +
 drivers/leds/ledtrig-cpu.c |  144 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/leds.h       |   15 +++++
 4 files changed, 170 insertions(+), 0 deletions(-)
 create mode 100644 drivers/leds/ledtrig-cpu.c

Comments

Eric Miao July 6, 2011, 1:16 p.m. UTC | #1
On Wed, Jul 6, 2011 at 8:34 PM, Bryan Wu <bryan.wu@canonical.com> wrote:
> 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@canonical.com:
> It moves arch/arm/kernel/leds.c 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 <rpurdie@rpsys.net>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
> ---
>  drivers/leds/Kconfig       |   10 +++
>  drivers/leds/Makefile      |    1 +
>  drivers/leds/ledtrig-cpu.c |  144 ++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/leds.h       |   15 +++++
>  4 files changed, 170 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/leds/ledtrig-cpu.c
>
> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
> index 713d43b..186000a 100644
> --- a/drivers/leds/Kconfig
> +++ b/drivers/leds/Kconfig
> @@ -446,6 +446,16 @@ config LEDS_TRIGGER_BACKLIGHT
>
>          If unsure, say N.
>
> +config LEDS_TRIGGER_CPU
> +       bool "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 what
> +         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 bbfd2e3..5e70d2e 100644
> --- a/drivers/leds/Makefile
> +++ b/drivers/leds/Makefile
> @@ -53,4 +53,5 @@ 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..4d63ada
> --- /dev/null
> +++ b/drivers/leds/ledtrig-cpu.c
> @@ -0,0 +1,144 @@
> +/*
> + * ledtrig-cpu.c - LED trigger based on CPU activity
> + *
> + * Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
> + * Copyright 2011 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 "leds.h"
> +
> +struct cpu_trig_data {
> +       struct led_classdev *led;
> +};
> +
> +static DEFINE_PER_CPU(struct cpu_trig_data *, cpu_triggers);
> +
> +void ledtrig_cpu(enum cpu_led_event ledevt)
> +{
> +       struct cpu_trig_data *trigdata = __get_cpu_var(cpu_triggers);
> +
> +       if (!trigdata)
> +               return;
> +
> +       /* Locate the correct CPU LED */
> +
> +       switch (ledevt) {
> +       case CPU_LED_START:
> +       case CPU_LED_IDLE_START:
> +               /* Will turn the LED on, max brightness */
> +               if (trigdata->led)
> +                       led_set_brightness(trigdata->led,
> +                                          trigdata->led->max_brightness);
> +               break;
> +
> +       case CPU_LED_STOP:
> +       case CPU_LED_IDLE_END:
> +       case CPU_LED_HALTED:
> +               /* Will turn the LED off */
> +               if (trigdata->led)
> +                       led_set_brightness(trigdata->led, LED_OFF);
> +               break;
> +
> +       default:
> +               /* Will leave the LED as it is */
> +               break;
> +       }
> +}

I'm a bit worrying about the LED brightness hardcoded here, what if
a platform requires different behavior, e.g. LED_OFF when IDLE_START.

> +EXPORT_SYMBOL(ledtrig_cpu);
> +
> +static void cpu_trig_activate_cpu(void *data)
> +{
> +       struct cpu_trig_data *cpu_data;
> +       struct led_classdev *led = data;
> +       int my_cpu = smp_processor_id();
> +       unsigned long target_cpu = (unsigned long) led->trigger_data;
> +
> +       if (target_cpu != my_cpu)
> +               return;
> +
> +       cpu_data = kzalloc(sizeof(*cpu_data), GFP_KERNEL);
> +       if (!cpu_data)
> +               return;
> +
> +       dev_info(led->dev, "led %s indicate activity on CPU %d\n",
> +                led->name, my_cpu);
> +
> +       cpu_data->led = led;
> +       __get_cpu_var(cpu_triggers) = cpu_data;
> +}
> +
> +static void cpu_trig_activate(struct led_classdev *led)
> +{
> +       on_each_cpu(cpu_trig_activate_cpu, led, 1);
> +}
> +
> +static void cpu_trig_deactivate(struct led_classdev *led)
> +{
> +       struct cpu_trig_data *cpu_data = led->trigger_data;
> +
> +       kfree(cpu_data);
> +}
> +
> +static struct led_trigger cpu_led_trigger = {
> +       .name           = "cpu",
> +       .activate       = cpu_trig_activate,
> +       .deactivate     = cpu_trig_deactivate,
> +};
> +
> +
> +static int cpu_syscore_suspend(void)
> +{
> +       ledtrig_cpu(CPU_LED_STOP);
> +       return 0;
> +}
> +
> +static void cpu_syscore_resume(void)
> +{
> +       ledtrig_cpu(CPU_LED_START);
> +}
> +
> +static void cpu_syscore_shutdown(void)
> +{
> +       ledtrig_cpu(CPU_LED_HALTED);
> +}
> +
> +static struct syscore_ops cpu_syscore_ops = {
> +       .shutdown       = cpu_syscore_shutdown,
> +       .suspend        = cpu_syscore_suspend,
> +       .resume         = cpu_syscore_resume,
> +};

Even this is static, I think naming of ledtrig_cpu_syscore_* will be better
here, causing less confusion. As cpu_syscore_shutdown really gave me a
first impression it's about the action when the CPU shuts down.

> +
> +static int __init cpu_trig_init(void)
> +{
> +       int ret;
> +
> +       ret = led_trigger_register(&cpu_led_trigger);
> +       if (!ret)
> +               register_syscore_ops(&cpu_syscore_ops);
> +
> +       return ret;
> +}
> +module_init(cpu_trig_init);
> +
> +static void __exit cpu_trig_exit(void)
> +{
> +       unregister_syscore_ops(&cpu_syscore_ops);
> +       led_trigger_unregister(&cpu_led_trigger);
> +}
> +module_exit(cpu_trig_exit);

ledtrig_cpu_exit?

> +
> +MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
> +MODULE_AUTHOR("Bryan Wu <bryan.wu@canonical.com>");
> +MODULE_DESCRIPTION("CPU LED trigger");
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index 5884def..94cdb9a 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -210,4 +210,19 @@ struct gpio_led_platform_data {
>  struct platform_device *gpio_led_register_device(
>                int id, const struct gpio_led_platform_data *pdata);
>
> +#ifdef CONFIG_LEDS_TRIGGER_CPU
> +enum cpu_led_event {
> +       CPU_LED_IDLE_START,
> +       CPU_LED_IDLE_END,
> +       CPU_LED_START,
> +       CPU_LED_STOP,
> +       CPU_LED_HALTED
> +};

A brief block of comments explaining these events would be
very helpful for passing correct parameters to ledtrig_cpu()

> +
> +/* Use this routine to handle LEDs */
> +extern void ledtrig_cpu(enum cpu_led_event evt);
> +#else
> +#define ledtrig_cpu(evt) do {} while (0)
> +#endif
> +
>  #endif         /* __LINUX_LEDS_H_INCLUDED */
> --
> 1.7.5
>
>
Russell King - ARM Linux July 6, 2011, 1:35 p.m. UTC | #2
On Wed, Jul 06, 2011 at 09:16:47PM +0800, Eric Miao wrote:
> On Wed, Jul 6, 2011 at 8:34 PM, Bryan Wu <bryan.wu@canonical.com> wrote:
> > +       switch (ledevt) {
> > +       case CPU_LED_START:
> > +       case CPU_LED_IDLE_START:
> > +               /* Will turn the LED on, max brightness */
> > +               if (trigdata->led)
> > +                       led_set_brightness(trigdata->led,
> > +                                          trigdata->led->max_brightness);
> > +               break;
> > +
> > +       case CPU_LED_STOP:
> > +       case CPU_LED_IDLE_END:
> > +       case CPU_LED_HALTED:
> > +               /* Will turn the LED off */
> > +               if (trigdata->led)
> > +                       led_set_brightness(trigdata->led, LED_OFF);
> > +               break;
> > +
> > +       default:
> > +               /* Will leave the LED as it is */
> > +               break;
> > +       }
> > +}
> 
> I'm a bit worrying about the LED brightness hardcoded here, what if
> a platform requires different behavior, e.g. LED_OFF when IDLE_START.

Indeed - there are platforms (Netwinder, Assabet etc) which use LED=ON
to mean that the system is not idle - and also turn the LED on when
halted.

A change of behaviour could be fairly disasterous too.  Eg, some people
use Netwinders in a stand-alone mode, and getting the LED behaviour correct
is _critical_ as it is the only display that some people may see - and
they may use that display to decide whether they can pull the power after
shutdown.  Changing it may mean that they end up pulling the power while
the system is still alive.
Nicolas Pitre July 6, 2011, 2:11 p.m. UTC | #3
On Wed, 6 Jul 2011, Russell King - ARM Linux wrote:

> On Wed, Jul 06, 2011 at 09:16:47PM +0800, Eric Miao wrote:
> > On Wed, Jul 6, 2011 at 8:34 PM, Bryan Wu <bryan.wu@canonical.com> wrote:
> > > +       switch (ledevt) {
> > > +       case CPU_LED_START:
> > > +       case CPU_LED_IDLE_START:
> > > +               /* Will turn the LED on, max brightness */
> > > +               if (trigdata->led)
> > > +                       led_set_brightness(trigdata->led,
> > > +                                          trigdata->led->max_brightness);
> > > +               break;
> > > +
> > > +       case CPU_LED_STOP:
> > > +       case CPU_LED_IDLE_END:
> > > +       case CPU_LED_HALTED:
> > > +               /* Will turn the LED off */
> > > +               if (trigdata->led)
> > > +                       led_set_brightness(trigdata->led, LED_OFF);
> > > +               break;
> > > +
> > > +       default:
> > > +               /* Will leave the LED as it is */
> > > +               break;
> > > +       }
> > > +}
> > 
> > I'm a bit worrying about the LED brightness hardcoded here, what if
> > a platform requires different behavior, e.g. LED_OFF when IDLE_START.
> 
> Indeed - there are platforms (Netwinder, Assabet etc) which use LED=ON
> to mean that the system is not idle - and also turn the LED on when
> halted.

What about simply setting active_low to 1 in the struct gpio_led 
instance for those particular LEDs (or invert it if it is already set)?


Nicolas
Bryan Wu July 7, 2011, 12:58 p.m. UTC | #4
On Wed, Jul 6, 2011 at 9:16 PM, Eric Miao <eric.y.miao@gmail.com> wrote:
> On Wed, Jul 6, 2011 at 8:34 PM, Bryan Wu <bryan.wu@canonical.com> wrote:
>> 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@canonical.com:
>> It moves arch/arm/kernel/leds.c 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 <rpurdie@rpsys.net>
>> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
>> Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
>> ---
>>  drivers/leds/Kconfig       |   10 +++
>>  drivers/leds/Makefile      |    1 +
>>  drivers/leds/ledtrig-cpu.c |  144 ++++++++++++++++++++++++++++++++++++++++++++
>>  include/linux/leds.h       |   15 +++++
>>  4 files changed, 170 insertions(+), 0 deletions(-)
>>  create mode 100644 drivers/leds/ledtrig-cpu.c
>>
>> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
>> index 713d43b..186000a 100644
>> --- a/drivers/leds/Kconfig
>> +++ b/drivers/leds/Kconfig
>> @@ -446,6 +446,16 @@ config LEDS_TRIGGER_BACKLIGHT
>>
>>          If unsure, say N.
>>
>> +config LEDS_TRIGGER_CPU
>> +       bool "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 what
>> +         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 bbfd2e3..5e70d2e 100644
>> --- a/drivers/leds/Makefile
>> +++ b/drivers/leds/Makefile
>> @@ -53,4 +53,5 @@ 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..4d63ada
>> --- /dev/null
>> +++ b/drivers/leds/ledtrig-cpu.c
>> @@ -0,0 +1,144 @@
>> +/*
>> + * ledtrig-cpu.c - LED trigger based on CPU activity
>> + *
>> + * Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
>> + * Copyright 2011 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 "leds.h"
>> +
>> +struct cpu_trig_data {
>> +       struct led_classdev *led;
>> +};
>> +
>> +static DEFINE_PER_CPU(struct cpu_trig_data *, cpu_triggers);
>> +
>> +void ledtrig_cpu(enum cpu_led_event ledevt)
>> +{
>> +       struct cpu_trig_data *trigdata = __get_cpu_var(cpu_triggers);
>> +
>> +       if (!trigdata)
>> +               return;
>> +
>> +       /* Locate the correct CPU LED */
>> +
>> +       switch (ledevt) {
>> +       case CPU_LED_START:
>> +       case CPU_LED_IDLE_START:
>> +               /* Will turn the LED on, max brightness */
>> +               if (trigdata->led)
>> +                       led_set_brightness(trigdata->led,
>> +                                          trigdata->led->max_brightness);
>> +               break;
>> +
>> +       case CPU_LED_STOP:
>> +       case CPU_LED_IDLE_END:
>> +       case CPU_LED_HALTED:
>> +               /* Will turn the LED off */
>> +               if (trigdata->led)
>> +                       led_set_brightness(trigdata->led, LED_OFF);
>> +               break;
>> +
>> +       default:
>> +               /* Will leave the LED as it is */
>> +               break;
>> +       }
>> +}
>
> I'm a bit worrying about the LED brightness hardcoded here, what if
> a platform requires different behavior, e.g. LED_OFF when IDLE_START.
>
>> +EXPORT_SYMBOL(ledtrig_cpu);
>> +
>> +static void cpu_trig_activate_cpu(void *data)
>> +{
>> +       struct cpu_trig_data *cpu_data;
>> +       struct led_classdev *led = data;
>> +       int my_cpu = smp_processor_id();
>> +       unsigned long target_cpu = (unsigned long) led->trigger_data;
>> +
>> +       if (target_cpu != my_cpu)
>> +               return;
>> +
>> +       cpu_data = kzalloc(sizeof(*cpu_data), GFP_KERNEL);
>> +       if (!cpu_data)
>> +               return;
>> +
>> +       dev_info(led->dev, "led %s indicate activity on CPU %d\n",
>> +                led->name, my_cpu);
>> +
>> +       cpu_data->led = led;
>> +       __get_cpu_var(cpu_triggers) = cpu_data;
>> +}
>> +
>> +static void cpu_trig_activate(struct led_classdev *led)
>> +{
>> +       on_each_cpu(cpu_trig_activate_cpu, led, 1);
>> +}
>> +
>> +static void cpu_trig_deactivate(struct led_classdev *led)
>> +{
>> +       struct cpu_trig_data *cpu_data = led->trigger_data;
>> +
>> +       kfree(cpu_data);
>> +}
>> +
>> +static struct led_trigger cpu_led_trigger = {
>> +       .name           = "cpu",
>> +       .activate       = cpu_trig_activate,
>> +       .deactivate     = cpu_trig_deactivate,
>> +};
>> +
>> +
>> +static int cpu_syscore_suspend(void)
>> +{
>> +       ledtrig_cpu(CPU_LED_STOP);
>> +       return 0;
>> +}
>> +
>> +static void cpu_syscore_resume(void)
>> +{
>> +       ledtrig_cpu(CPU_LED_START);
>> +}
>> +
>> +static void cpu_syscore_shutdown(void)
>> +{
>> +       ledtrig_cpu(CPU_LED_HALTED);
>> +}
>> +
>> +static struct syscore_ops cpu_syscore_ops = {
>> +       .shutdown       = cpu_syscore_shutdown,
>> +       .suspend        = cpu_syscore_suspend,
>> +       .resume         = cpu_syscore_resume,
>> +};
>
> Even this is static, I think naming of ledtrig_cpu_syscore_* will be better
> here, causing less confusion. As cpu_syscore_shutdown really gave me a
> first impression it's about the action when the CPU shuts down.
>

OK, I will fix this name confusing issue.
Thanks

>> +
>> +static int __init cpu_trig_init(void)
>> +{
>> +       int ret;
>> +
>> +       ret = led_trigger_register(&cpu_led_trigger);
>> +       if (!ret)
>> +               register_syscore_ops(&cpu_syscore_ops);
>> +
>> +       return ret;
>> +}
>> +module_init(cpu_trig_init);
>> +
>> +static void __exit cpu_trig_exit(void)
>> +{
>> +       unregister_syscore_ops(&cpu_syscore_ops);
>> +       led_trigger_unregister(&cpu_led_trigger);
>> +}
>> +module_exit(cpu_trig_exit);
>
> ledtrig_cpu_exit?
>
>> +
>> +MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
>> +MODULE_AUTHOR("Bryan Wu <bryan.wu@canonical.com>");
>> +MODULE_DESCRIPTION("CPU LED trigger");
>> +MODULE_LICENSE("GPL");
>> diff --git a/include/linux/leds.h b/include/linux/leds.h
>> index 5884def..94cdb9a 100644
>> --- a/include/linux/leds.h
>> +++ b/include/linux/leds.h
>> @@ -210,4 +210,19 @@ struct gpio_led_platform_data {
>>  struct platform_device *gpio_led_register_device(
>>                int id, const struct gpio_led_platform_data *pdata);
>>
>> +#ifdef CONFIG_LEDS_TRIGGER_CPU
>> +enum cpu_led_event {
>> +       CPU_LED_IDLE_START,
>> +       CPU_LED_IDLE_END,
>> +       CPU_LED_START,
>> +       CPU_LED_STOP,
>> +       CPU_LED_HALTED
>> +};
>
> A brief block of comments explaining these events would be
> very helpful for passing correct parameters to ledtrig_cpu()
>
>> +
>> +/* Use this routine to handle LEDs */
>> +extern void ledtrig_cpu(enum cpu_led_event evt);
>> +#else
>> +#define ledtrig_cpu(evt) do {} while (0)
>> +#endif
>> +
>>  #endif         /* __LINUX_LEDS_H_INCLUDED */
>> --
>> 1.7.5
>>
>>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
diff mbox

Patch

diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 713d43b..186000a 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -446,6 +446,16 @@  config LEDS_TRIGGER_BACKLIGHT
 
 	  If unsure, say N.
 
+config LEDS_TRIGGER_CPU
+	bool "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 what
+	  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 bbfd2e3..5e70d2e 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile
@@ -53,4 +53,5 @@  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..4d63ada
--- /dev/null
+++ b/drivers/leds/ledtrig-cpu.c
@@ -0,0 +1,144 @@ 
+/*
+ * ledtrig-cpu.c - LED trigger based on CPU activity
+ *
+ * Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
+ * Copyright 2011 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 "leds.h"
+
+struct cpu_trig_data {
+	struct led_classdev *led;
+};
+
+static DEFINE_PER_CPU(struct cpu_trig_data *, cpu_triggers);
+
+void ledtrig_cpu(enum cpu_led_event ledevt)
+{
+	struct cpu_trig_data *trigdata = __get_cpu_var(cpu_triggers);
+
+	if (!trigdata)
+		return;
+
+	/* Locate the correct CPU LED */
+
+	switch (ledevt) {
+	case CPU_LED_START:
+	case CPU_LED_IDLE_START:
+		/* Will turn the LED on, max brightness */
+		if (trigdata->led)
+			led_set_brightness(trigdata->led,
+					   trigdata->led->max_brightness);
+		break;
+
+	case CPU_LED_STOP:
+	case CPU_LED_IDLE_END:
+	case CPU_LED_HALTED:
+		/* Will turn the LED off */
+		if (trigdata->led)
+			led_set_brightness(trigdata->led, LED_OFF);
+		break;
+
+	default:
+		/* Will leave the LED as it is */
+		break;
+	}
+}
+EXPORT_SYMBOL(ledtrig_cpu);
+
+static void cpu_trig_activate_cpu(void *data)
+{
+	struct cpu_trig_data *cpu_data;
+	struct led_classdev *led = data;
+	int my_cpu = smp_processor_id();
+	unsigned long target_cpu = (unsigned long) led->trigger_data;
+
+	if (target_cpu != my_cpu)
+		return;
+
+	cpu_data = kzalloc(sizeof(*cpu_data), GFP_KERNEL);
+	if (!cpu_data)
+		return;
+
+	dev_info(led->dev, "led %s indicate activity on CPU %d\n",
+		 led->name, my_cpu);
+
+	cpu_data->led = led;
+	__get_cpu_var(cpu_triggers) = cpu_data;
+}
+
+static void cpu_trig_activate(struct led_classdev *led)
+{
+	on_each_cpu(cpu_trig_activate_cpu, led, 1);
+}
+
+static void cpu_trig_deactivate(struct led_classdev *led)
+{
+	struct cpu_trig_data *cpu_data = led->trigger_data;
+
+	kfree(cpu_data);
+}
+
+static struct led_trigger cpu_led_trigger = {
+	.name		= "cpu",
+	.activate	= cpu_trig_activate,
+	.deactivate	= cpu_trig_deactivate,
+};
+
+
+static int cpu_syscore_suspend(void)
+{
+	ledtrig_cpu(CPU_LED_STOP);
+	return 0;
+}
+
+static void cpu_syscore_resume(void)
+{
+	ledtrig_cpu(CPU_LED_START);
+}
+
+static void cpu_syscore_shutdown(void)
+{
+	ledtrig_cpu(CPU_LED_HALTED);
+}
+
+static struct syscore_ops cpu_syscore_ops = {
+	.shutdown	= cpu_syscore_shutdown,
+	.suspend	= cpu_syscore_suspend,
+	.resume		= cpu_syscore_resume,
+};
+
+static int __init cpu_trig_init(void)
+{
+	int ret;
+
+	ret = led_trigger_register(&cpu_led_trigger);
+	if (!ret)
+		register_syscore_ops(&cpu_syscore_ops);
+
+	return ret;
+}
+module_init(cpu_trig_init);
+
+static void __exit cpu_trig_exit(void)
+{
+	unregister_syscore_ops(&cpu_syscore_ops);
+	led_trigger_unregister(&cpu_led_trigger);
+}
+module_exit(cpu_trig_exit);
+
+MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
+MODULE_AUTHOR("Bryan Wu <bryan.wu@canonical.com>");
+MODULE_DESCRIPTION("CPU LED trigger");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 5884def..94cdb9a 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -210,4 +210,19 @@  struct gpio_led_platform_data {
 struct platform_device *gpio_led_register_device(
 		int id, const struct gpio_led_platform_data *pdata);
 
+#ifdef CONFIG_LEDS_TRIGGER_CPU
+enum cpu_led_event {
+	CPU_LED_IDLE_START,
+	CPU_LED_IDLE_END,
+	CPU_LED_START,
+	CPU_LED_STOP,
+	CPU_LED_HALTED
+};
+
+/* Use this routine to handle LEDs */
+extern void ledtrig_cpu(enum cpu_led_event evt);
+#else
+#define ledtrig_cpu(evt) do {} while (0)
+#endif
+
 #endif		/* __LINUX_LEDS_H_INCLUDED */