PATCH: Create new LED trigger for CPU activity (ledtrig-cpu)

["Thomas Tuttle" <thinkinginbinary+lkml@gmail.com>]

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Here is a patch I wrote that creates a new LED trigger for CPU
activity.  It creates a new config option, CONFIG_LEDS_TRIGGER_CPU, as
well as four suboptions to select the combination of user, nice,
system, and iowait that should turn the LED on.

It's loosely based on the ledtrig-ide-disk plugin, but only for
general guidance.  It doesn't modify anything in the CPU scheduling
code, for better or for worse; it is less efficient, because it checks
the CPU time every 5ms instead of "knowing" when the CPU is idle or
active, but it doesn't require changes to any other code, and is much
less hairy for not digging into the scheduling stuff.  (It's also more
flexible, because it can deal with user/nice/system/iowait time
without much effort.)

The same disclaimers from my last email (the asus_acpi LED support
one) apply--I haven't written much kernel code; this is diffed against
2.6.17.1, not .3, but I don't think anything has changed; I've tested
it, but no guarantees it's perfect; and I apologize for the MIME type
of text/x-patch, but it should work.

Constructive comments would be greatly appreciated.

-- 
Thomas Tuttle
http://thinkinginbinary.webhop.net/
thinkinginbinary@gmail.com
AIM: thinkinginbinary

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diff -udrN linux-2.6.17.1/drivers/leds/Kconfig linux-2.6.17.1-mine/drivers/leds/Kconfig
--- linux-2.6.17.1/drivers/leds/Kconfig	2006-07-05 19:39:25.000000000 -0400
+++ linux-2.6.17.1-mine/drivers/leds/Kconfig	2006-07-05 21:04:37.000000000 -0400
@@ -80,6 +80,37 @@
 	  This allows LEDs to be controlled by a programmable timer
 	  via sysfs. If unsure, say Y.
 
+config LEDS_TRIGGER_CPU
+	tristate "LED CPU Trigger"
+	depends LEDS_TRIGGERS
+	help
+	  This allows LEDs to be controlled by CPU activity.
+	  If unsure, say Y.
+
+config LEDS_TRIGGER_CPU_INCLUDE_USER
+	bool "Include user time in CPU trigger"
+	depends LEDS_TRIGGER_CPU
+	help
+	  This option makes user CPU time cause the CPU trigger to activate.
+
+config LEDS_TRIGGER_CPU_INCLUDE_NICE
+	bool "Include nice time in CPU trigger"
+	depends LEDS_TRIGGER_CPU
+	help
+	  This option makes nice CPU time cause the CPU trigger to activate.
+
+config LEDS_TRIGGER_CPU_INCLUDE_SYSTEM
+	bool "Include system time in CPU trigger"
+	depends LEDS_TRIGGER_CPU
+	help
+	  This option makes system CPU time cause the CPU trigger to activate.
+
+config LEDS_TRIGGER_CPU_INCLUDE_IOWAIT
+	bool "Include iowait time in CPU trigger"
+	depends LEDS_TRIGGER_CPU
+	help
+	  This option makes iowait CPU time cause the CPU trigger to activate.
+
 config LEDS_TRIGGER_IDE_DISK
 	bool "LED IDE Disk Trigger"
 	depends LEDS_TRIGGERS && BLK_DEV_IDEDISK
diff -udrN linux-2.6.17.1/drivers/leds/ledtrig-cpu.c linux-2.6.17.1-mine/drivers/leds/ledtrig-cpu.c
--- linux-2.6.17.1/drivers/leds/ledtrig-cpu.c	1969-12-31 19:00:00.000000000 -0500
+++ linux-2.6.17.1-mine/drivers/leds/ledtrig-cpu.c	2006-07-05 21:01:54.000000000 -0400
@@ -0,0 +1,90 @@
+/*
+ * LED CPU Activity Trigger
+ *
+ * Copyright 2006 Thomas Tuttle
+ *
+ * Author: Thomas Tuttle <thinkinginbinary@gmail.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/config.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/timer.h>
+#include <linux/leds.h>
+#include <linux/kernel_stat.h>
+#include <asm/cputime.h>
+
+#define UPDATE_INTERVAL (5) // ms
+
+static void ledtrig_cpu_timerfunc(unsigned long data);
+
+DEFINE_LED_TRIGGER(ledtrig_cpu);
+static DEFINE_TIMER(ledtrig_cpu_timer, ledtrig_cpu_timerfunc, 0, 0);
+
+static cputime64_t cpu_usage(void) {
+	int i;
+	cputime64_t user, nice, system, idle, iowait, total;
+	user = nice = system = idle = iowait = total = cputime64_zero;
+
+	for_each_possible_cpu(i) {
+		user = cputime64_add(user, kstat_cpu(i).cpustat.user);
+		nice = cputime64_add(nice, kstat_cpu(i).cpustat.nice);
+		system = cputime64_add(system, kstat_cpu(i).cpustat.system);
+		idle = cputime64_add(idle, kstat_cpu(i).cpustat.idle);
+		iowait = cputime64_add(iowait, kstat_cpu(i).cpustat.iowait);
+	}
+
+#ifdef CONFIG_LEDS_TRIGGER_CPU_INCLUDE_USER
+	total = cputime64_add(total, user);
+#endif
+#ifdef CONFIG_LEDS_TRIGGER_CPU_INCLUDE_NICE
+	total = cputime64_add(total, nice);
+#endif
+#ifdef CONFIG_LEDS_TRIGGER_CPU_INCLUDE_SYSTEM
+	total = cputime64_add(total, system);
+#endif
+#ifdef CONFIG_LEDS_TRIGGER_CPU_INCLUDE_IOWAIT
+	total = cputime64_add(total, iowait);
+#endif
+
+	return total;
+}
+
+cputime64_t last_cputime;
+
+static void ledtrig_cpu_timerfunc(unsigned long data) {
+	cputime64_t this_cputime = cpu_usage();
+	cputime64_t used_cputime = this_cputime - last_cputime;
+	if (used_cputime > 0) {
+		led_trigger_event(ledtrig_cpu, LED_FULL);
+	} else {
+		led_trigger_event(ledtrig_cpu, LED_OFF);
+	}
+	last_cputime = cpu_usage();
+	mod_timer(&ledtrig_cpu_timer, jiffies + msecs_to_jiffies(UPDATE_INTERVAL));
+}
+
+static int __init ledtrig_cpu_init(void) {
+	led_trigger_register_simple("cpu", &ledtrig_cpu);
+	last_cputime = cpu_usage();
+	mod_timer(&ledtrig_cpu_timer, jiffies + msecs_to_jiffies(UPDATE_INTERVAL));
+	return 0;
+}
+
+static void __exit ledtrig_cpu_exit(void) {
+	del_timer(&ledtrig_cpu_timer);
+	led_trigger_unregister_simple(ledtrig_cpu);
+}
+
+module_init(ledtrig_cpu_init);
+module_exit(ledtrig_cpu_exit);
+
+MODULE_AUTHOR("Thomas Tuttle <thinkinginbinary@gmail.com>");
+MODULE_DESCRIPTION("LED CPU Activity Trigger");
+MODULE_LICENSE("GPL");
diff -udrN linux-2.6.17.1/drivers/leds/Makefile linux-2.6.17.1-mine/drivers/leds/Makefile
--- linux-2.6.17.1/drivers/leds/Makefile	2006-07-05 19:39:25.000000000 -0400
+++ linux-2.6.17.1-mine/drivers/leds/Makefile	2006-07-05 21:07:27.000000000 -0400
@@ -15,3 +15,4 @@
 # LED Triggers
 obj-$(CONFIG_LEDS_TRIGGER_TIMER)	+= ledtrig-timer.o
 obj-$(CONFIG_LEDS_TRIGGER_IDE_DISK)	+= ledtrig-ide-disk.o
+obj-$(CONFIG_LEDS_TRIGGER_CPU)		+= ledtrig-cpu.o