drivers/macintosh/windfarm_core.c - arm/linux - Git at Google

 /*
  * Windfarm PowerMac thermal control. Core
  *
  * (c) Copyright 2005 Benjamin Herrenschmidt, IBM Corp.
  *                    <benh@kernel.crashing.org>
  *
  * Released under the term of the GNU GPL v2.
  *
  * This core code tracks the list of sensors & controls, register
  * clients, and holds the kernel thread used for control.
  *
  * TODO:
  *
  * Add some information about sensor/control type and data format to
  * sensors/controls, and have the sysfs attribute stuff be moved
  * generically here instead of hard coded in the platform specific
  * driver as it us currently
  *
  * This however requires solving some annoying lifetime issues with
  * sysfs which doesn't seem to have lifetime rules for struct attribute,
  * I may have to create full features kobjects for every sensor/control
  * instead which is a bit of an overkill imho
  */

 #include <linux/types.h>
 #include <linux/errno.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/spinlock.h>
 #include <linux/kthread.h>
 #include <linux/jiffies.h>
 #include <linux/reboot.h>
 #include <linux/device.h>
 #include <linux/platform_device.h>
 #include <linux/mutex.h>
 #include <linux/freezer.h>

 #include <asm/prom.h>

 #include "windfarm.h"

 #define VERSION "0.2"

 #undef DEBUG

 #ifdef DEBUG
 #define DBG(args...)	printk(args)
 #else
 #define DBG(args...)	do { } while(0)
 #endif

 static LIST_HEAD(wf_controls);
 static LIST_HEAD(wf_sensors);
 static DEFINE_MUTEX(wf_lock);
 static BLOCKING_NOTIFIER_HEAD(wf_client_list);
 static int wf_client_count;
 static unsigned int wf_overtemp;
 static unsigned int wf_overtemp_counter;
 struct task_struct *wf_thread;

 static struct platform_device wf_platform_device = {
 	.name	= "windfarm",
 };

 /*
  * Utilities & tick thread
  */

 static inline void wf_notify(int event, void *param)
 {
 	blocking_notifier_call_chain(&wf_client_list, event, param);
 }

 static int wf_critical_overtemp(void)
 {
 	static char const critical_overtemp_path[] = "/sbin/critical_overtemp";
 	char *argv[] = { (char *)critical_overtemp_path, NULL };
 	static char *envp[] = { "HOME=/",
 				"TERM=linux",
 				"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
 				NULL };

 	return call_usermodehelper(critical_overtemp_path,
 				   argv, envp, UMH_WAIT_EXEC);
 }

 static int wf_thread_func(void *data)
 {
 	unsigned long next, delay;

 	next = jiffies;

 	DBG("wf: thread started\n");

 	set_freezable();
 	while (!kthread_should_stop()) {
 		try_to_freeze();

 		if (time_after_eq(jiffies, next)) {
 			wf_notify(WF_EVENT_TICK, NULL);
 			if (wf_overtemp) {
 				wf_overtemp_counter++;
 				/* 10 seconds overtemp, notify userland */
 				if (wf_overtemp_counter > 10)
 					wf_critical_overtemp();
 				/* 30 seconds, shutdown */
 				if (wf_overtemp_counter > 30) {
 					printk(KERN_ERR "windfarm: Overtemp "
 					       "for more than 30"
 					       " seconds, shutting down\n");
 					machine_power_off();
 				}
 			}
 			next += HZ;
 		}

 		delay = next - jiffies;
 		if (delay <= HZ)
 			schedule_timeout_interruptible(delay);
 	}

 	DBG("wf: thread stopped\n");

 	return 0;
 }

 static void wf_start_thread(void)
 {
 	wf_thread = kthread_run(wf_thread_func, NULL, "kwindfarm");
 	if (IS_ERR(wf_thread)) {
 		printk(KERN_ERR "windfarm: failed to create thread,err %ld\n",
 		       PTR_ERR(wf_thread));
 		wf_thread = NULL;
 	}
 }


 static void wf_stop_thread(void)
 {
 	if (wf_thread)
 		kthread_stop(wf_thread);
 	wf_thread = NULL;
 }

 /*
  * Controls
  */

 static void wf_control_release(struct kref *kref)
 {
 	struct wf_control *ct = container_of(kref, struct wf_control, ref);

 	DBG("wf: Deleting control %s\n", ct->name);

 	if (ct->ops && ct->ops->release)
 		ct->ops->release(ct);
 	else
 		kfree(ct);
 }

 static ssize_t wf_show_control(struct device *dev,
 			       struct device_attribute *attr, char *buf)
 {
 	struct wf_control *ctrl = container_of(attr, struct wf_control, attr);
 	const char *typestr;
 	s32 val = 0;
 	int err;

 	err = ctrl->ops->get_value(ctrl, &val);
 	if (err < 0) {
 		if (err == -EFAULT)
 			return sprintf(buf, "<HW FAULT>\n");
 		return err;
 	}
 	switch(ctrl->type) {
 	case WF_CONTROL_RPM_FAN:
 		typestr = " RPM";
 		break;
 	case WF_CONTROL_PWM_FAN:
 		typestr = " %";
 		break;
 	default:
 		typestr = "";
 	}
 	return sprintf(buf, "%d%s\n", val, typestr);
 }

 /* This is really only for debugging... */
 static ssize_t wf_store_control(struct device *dev,
 				struct device_attribute *attr,
 				const char *buf, size_t count)
 {
 	struct wf_control *ctrl = container_of(attr, struct wf_control, attr);
 	int val;
 	int err;
 	char *endp;

 	val = simple_strtoul(buf, &endp, 0);
 	while (endp < buf + count && (*endp == ' ' || *endp == '\n'))
 		++endp;
 	if (endp - buf < count)
 		return -EINVAL;
 	err = ctrl->ops->set_value(ctrl, val);
 	if (err < 0)
 		return err;
 	return count;
 }

 int wf_register_control(struct wf_control *new_ct)
 {
 	struct wf_control *ct;

 	mutex_lock(&wf_lock);
 	list_for_each_entry(ct, &wf_controls, link) {
 		if (!strcmp(ct->name, new_ct->name)) {
 			printk(KERN_WARNING "windfarm: trying to register"
 			       " duplicate control %s\n", ct->name);
 			mutex_unlock(&wf_lock);
 			return -EEXIST;
 		}
 	}
 	kref_init(&new_ct->ref);
 	list_add(&new_ct->link, &wf_controls);

 	sysfs_attr_init(&new_ct->attr.attr);
 	new_ct->attr.attr.name = new_ct->name;
 	new_ct->attr.attr.mode = 0644;
 	new_ct->attr.show = wf_show_control;
 	new_ct->attr.store = wf_store_control;
 	if (device_create_file(&wf_platform_device.dev, &new_ct->attr))
 		printk(KERN_WARNING "windfarm: device_create_file failed"
 			" for %s\n", new_ct->name);
 		/* the subsystem still does useful work without the file */

 	DBG("wf: Registered control %s\n", new_ct->name);

 	wf_notify(WF_EVENT_NEW_CONTROL, new_ct);
 	mutex_unlock(&wf_lock);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(wf_register_control);

 void wf_unregister_control(struct wf_control *ct)
 {
 	mutex_lock(&wf_lock);
 	list_del(&ct->link);
 	mutex_unlock(&wf_lock);

 	DBG("wf: Unregistered control %s\n", ct->name);

 	kref_put(&ct->ref, wf_control_release);
 }
 EXPORT_SYMBOL_GPL(wf_unregister_control);

 int wf_get_control(struct wf_control *ct)
 {
 	if (!try_module_get(ct->ops->owner))
 		return -ENODEV;
 	kref_get(&ct->ref);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(wf_get_control);

 void wf_put_control(struct wf_control *ct)
 {
 	struct module *mod = ct->ops->owner;
 	kref_put(&ct->ref, wf_control_release);
 	module_put(mod);
 }
 EXPORT_SYMBOL_GPL(wf_put_control);


 /*
  * Sensors
  */


 static void wf_sensor_release(struct kref *kref)
 {
 	struct wf_sensor *sr = container_of(kref, struct wf_sensor, ref);

 	DBG("wf: Deleting sensor %s\n", sr->name);

 	if (sr->ops && sr->ops->release)
 		sr->ops->release(sr);
 	else
 		kfree(sr);
 }

 static ssize_t wf_show_sensor(struct device *dev,
 			      struct device_attribute *attr, char *buf)
 {
 	struct wf_sensor *sens = container_of(attr, struct wf_sensor, attr);
 	s32 val = 0;
 	int err;

 	err = sens->ops->get_value(sens, &val);
 	if (err < 0)
 		return err;
 	return sprintf(buf, "%d.%03d\n", FIX32TOPRINT(val));
 }

 int wf_register_sensor(struct wf_sensor *new_sr)
 {
 	struct wf_sensor *sr;

 	mutex_lock(&wf_lock);
 	list_for_each_entry(sr, &wf_sensors, link) {
 		if (!strcmp(sr->name, new_sr->name)) {
 			printk(KERN_WARNING "windfarm: trying to register"
 			       " duplicate sensor %s\n", sr->name);
 			mutex_unlock(&wf_lock);
 			return -EEXIST;
 		}
 	}
 	kref_init(&new_sr->ref);
 	list_add(&new_sr->link, &wf_sensors);

 	sysfs_attr_init(&new_sr->attr.attr);
 	new_sr->attr.attr.name = new_sr->name;
 	new_sr->attr.attr.mode = 0444;
 	new_sr->attr.show = wf_show_sensor;
 	new_sr->attr.store = NULL;
 	if (device_create_file(&wf_platform_device.dev, &new_sr->attr))
 		printk(KERN_WARNING "windfarm: device_create_file failed"
 			" for %s\n", new_sr->name);
 		/* the subsystem still does useful work without the file */

 	DBG("wf: Registered sensor %s\n", new_sr->name);

 	wf_notify(WF_EVENT_NEW_SENSOR, new_sr);
 	mutex_unlock(&wf_lock);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(wf_register_sensor);

 void wf_unregister_sensor(struct wf_sensor *sr)
 {
 	mutex_lock(&wf_lock);
 	list_del(&sr->link);
 	mutex_unlock(&wf_lock);

 	DBG("wf: Unregistered sensor %s\n", sr->name);

 	wf_put_sensor(sr);
 }
 EXPORT_SYMBOL_GPL(wf_unregister_sensor);

 int wf_get_sensor(struct wf_sensor *sr)
 {
 	if (!try_module_get(sr->ops->owner))
 		return -ENODEV;
 	kref_get(&sr->ref);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(wf_get_sensor);

 void wf_put_sensor(struct wf_sensor *sr)
 {
 	struct module *mod = sr->ops->owner;
 	kref_put(&sr->ref, wf_sensor_release);
 	module_put(mod);
 }
 EXPORT_SYMBOL_GPL(wf_put_sensor);


 /*
  * Client & notification
  */

 int wf_register_client(struct notifier_block *nb)
 {
 	int rc;
 	struct wf_control *ct;
 	struct wf_sensor *sr;

 	mutex_lock(&wf_lock);
 	rc = blocking_notifier_chain_register(&wf_client_list, nb);
 	if (rc != 0)
 		goto bail;
 	wf_client_count++;
 	list_for_each_entry(ct, &wf_controls, link)
 		wf_notify(WF_EVENT_NEW_CONTROL, ct);
 	list_for_each_entry(sr, &wf_sensors, link)
 		wf_notify(WF_EVENT_NEW_SENSOR, sr);
 	if (wf_client_count == 1)
 		wf_start_thread();
  bail:
 	mutex_unlock(&wf_lock);
 	return rc;
 }
 EXPORT_SYMBOL_GPL(wf_register_client);

 int wf_unregister_client(struct notifier_block *nb)
 {
 	mutex_lock(&wf_lock);
 	blocking_notifier_chain_unregister(&wf_client_list, nb);
 	wf_client_count--;
 	if (wf_client_count == 0)
 		wf_stop_thread();
 	mutex_unlock(&wf_lock);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(wf_unregister_client);

 void wf_set_overtemp(void)
 {
 	mutex_lock(&wf_lock);
 	wf_overtemp++;
 	if (wf_overtemp == 1) {
 		printk(KERN_WARNING "windfarm: Overtemp condition detected !\n");
 		wf_overtemp_counter = 0;
 		wf_notify(WF_EVENT_OVERTEMP, NULL);
 	}
 	mutex_unlock(&wf_lock);
 }
 EXPORT_SYMBOL_GPL(wf_set_overtemp);

 void wf_clear_overtemp(void)
 {
 	mutex_lock(&wf_lock);
 	WARN_ON(wf_overtemp == 0);
 	if (wf_overtemp == 0) {
 		mutex_unlock(&wf_lock);
 		return;
 	}
 	wf_overtemp--;
 	if (wf_overtemp == 0) {
 		printk(KERN_WARNING "windfarm: Overtemp condition cleared !\n");
 		wf_notify(WF_EVENT_NORMALTEMP, NULL);
 	}
 	mutex_unlock(&wf_lock);
 }
 EXPORT_SYMBOL_GPL(wf_clear_overtemp);

 static int __init windfarm_core_init(void)
 {
 	DBG("wf: core loaded\n");

 	platform_device_register(&wf_platform_device);
 	return 0;
 }

 static void __exit windfarm_core_exit(void)
 {
 	BUG_ON(wf_client_count != 0);

 	DBG("wf: core unloaded\n");

 	platform_device_unregister(&wf_platform_device);
 }


 module_init(windfarm_core_init);
 module_exit(windfarm_core_exit);

 MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
 MODULE_DESCRIPTION("Core component of PowerMac thermal control");
 MODULE_LICENSE("GPL");
	/*
	* Windfarm PowerMac thermal control. Core
	*
	* (c) Copyright 2005 Benjamin Herrenschmidt, IBM Corp.
	* <benh@kernel.crashing.org>
	*
	* Released under the term of the GNU GPL v2.
	*
	* This core code tracks the list of sensors & controls, register
	* clients, and holds the kernel thread used for control.
	*
	* TODO:
	*
	* Add some information about sensor/control type and data format to
	* sensors/controls, and have the sysfs attribute stuff be moved
	* generically here instead of hard coded in the platform specific
	* driver as it us currently
	*
	* This however requires solving some annoying lifetime issues with
	* sysfs which doesn't seem to have lifetime rules for struct attribute,
	* I may have to create full features kobjects for every sensor/control
	* instead which is a bit of an overkill imho
	*/

	#include <linux/types.h>
	#include <linux/errno.h>
	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/init.h>
	#include <linux/spinlock.h>
	#include <linux/kthread.h>
	#include <linux/jiffies.h>
	#include <linux/reboot.h>
	#include <linux/device.h>
	#include <linux/platform_device.h>
	#include <linux/mutex.h>
	#include <linux/freezer.h>

	#include <asm/prom.h>

	#include "windfarm.h"

	#define VERSION "0.2"

	#undef DEBUG

	#ifdef DEBUG
	#define DBG(args...) printk(args)
	#else
	#define DBG(args...) do { } while(0)
	#endif

	static LIST_HEAD(wf_controls);
	static LIST_HEAD(wf_sensors);
	static DEFINE_MUTEX(wf_lock);
	static BLOCKING_NOTIFIER_HEAD(wf_client_list);
	static int wf_client_count;
	static unsigned int wf_overtemp;
	static unsigned int wf_overtemp_counter;
	struct task_struct *wf_thread;

	static struct platform_device wf_platform_device = {
	.name = "windfarm",
	};

	/*
	* Utilities & tick thread
	*/

	static inline void wf_notify(int event, void *param)
	{
	blocking_notifier_call_chain(&wf_client_list, event, param);
	}

	static int wf_critical_overtemp(void)
	{
	static char const critical_overtemp_path[] = "/sbin/critical_overtemp";
	char argv[] = { (char )critical_overtemp_path, NULL };
	static char *envp[] = { "HOME=/",
	"TERM=linux",
	"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
	NULL };

	return call_usermodehelper(critical_overtemp_path,
	argv, envp, UMH_WAIT_EXEC);
	}

	static int wf_thread_func(void *data)
	{
	unsigned long next, delay;

	next = jiffies;

	DBG("wf: thread started\n");

	set_freezable();
	while (!kthread_should_stop()) {
	try_to_freeze();

	if (time_after_eq(jiffies, next)) {
	wf_notify(WF_EVENT_TICK, NULL);
	if (wf_overtemp) {
	wf_overtemp_counter++;
	/* 10 seconds overtemp, notify userland */
	if (wf_overtemp_counter > 10)
	wf_critical_overtemp();
	/* 30 seconds, shutdown */
	if (wf_overtemp_counter > 30) {
	printk(KERN_ERR "windfarm: Overtemp "
	"for more than 30"
	" seconds, shutting down\n");
	machine_power_off();
	}
	}
	next += HZ;
	}

	delay = next - jiffies;
	if (delay <= HZ)
	schedule_timeout_interruptible(delay);
	}

	DBG("wf: thread stopped\n");

	return 0;
	}

	static void wf_start_thread(void)
	{
	wf_thread = kthread_run(wf_thread_func, NULL, "kwindfarm");
	if (IS_ERR(wf_thread)) {
	printk(KERN_ERR "windfarm: failed to create thread,err %ld\n",
	PTR_ERR(wf_thread));
	wf_thread = NULL;
	}
	}


	static void wf_stop_thread(void)
	{
	if (wf_thread)
	kthread_stop(wf_thread);
	wf_thread = NULL;
	}

	/*
	* Controls
	*/

	static void wf_control_release(struct kref *kref)
	{
	struct wf_control *ct = container_of(kref, struct wf_control, ref);

	DBG("wf: Deleting control %s\n", ct->name);

	if (ct->ops && ct->ops->release)
	ct->ops->release(ct);
	else
	kfree(ct);
	}

	static ssize_t wf_show_control(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct wf_control *ctrl = container_of(attr, struct wf_control, attr);
	const char *typestr;
	s32 val = 0;
	int err;

	err = ctrl->ops->get_value(ctrl, &val);
	if (err < 0) {
	if (err == -EFAULT)
	return sprintf(buf, "<HW FAULT>\n");
	return err;
	}
	switch(ctrl->type) {
	case WF_CONTROL_RPM_FAN:
	typestr = " RPM";
	break;
	case WF_CONTROL_PWM_FAN:
	typestr = " %";
	break;
	default:
	typestr = "";
	}
	return sprintf(buf, "%d%s\n", val, typestr);
	}

	/* This is really only for debugging... */
	static ssize_t wf_store_control(struct device *dev,
	struct device_attribute *attr,
	const char *buf, size_t count)
	{
	struct wf_control *ctrl = container_of(attr, struct wf_control, attr);
	int val;
	int err;
	char *endp;

	val = simple_strtoul(buf, &endp, 0);
	while (endp < buf + count && (endp == ' ' \|\| endp == '\n'))
	++endp;
	if (endp - buf < count)
	return -EINVAL;
	err = ctrl->ops->set_value(ctrl, val);
	if (err < 0)
	return err;
	return count;
	}

	int wf_register_control(struct wf_control *new_ct)
	{
	struct wf_control *ct;

	mutex_lock(&wf_lock);
	list_for_each_entry(ct, &wf_controls, link) {
	if (!strcmp(ct->name, new_ct->name)) {
	printk(KERN_WARNING "windfarm: trying to register"
	" duplicate control %s\n", ct->name);
	mutex_unlock(&wf_lock);
	return -EEXIST;
	}
	}
	kref_init(&new_ct->ref);
	list_add(&new_ct->link, &wf_controls);

	sysfs_attr_init(&new_ct->attr.attr);
	new_ct->attr.attr.name = new_ct->name;
	new_ct->attr.attr.mode = 0644;
	new_ct->attr.show = wf_show_control;
	new_ct->attr.store = wf_store_control;
	if (device_create_file(&wf_platform_device.dev, &new_ct->attr))
	printk(KERN_WARNING "windfarm: device_create_file failed"
	" for %s\n", new_ct->name);
	/* the subsystem still does useful work without the file */

	DBG("wf: Registered control %s\n", new_ct->name);

	wf_notify(WF_EVENT_NEW_CONTROL, new_ct);
	mutex_unlock(&wf_lock);

	return 0;
	}
	EXPORT_SYMBOL_GPL(wf_register_control);

	void wf_unregister_control(struct wf_control *ct)
	{
	mutex_lock(&wf_lock);
	list_del(&ct->link);
	mutex_unlock(&wf_lock);

	DBG("wf: Unregistered control %s\n", ct->name);

	kref_put(&ct->ref, wf_control_release);
	}
	EXPORT_SYMBOL_GPL(wf_unregister_control);

	int wf_get_control(struct wf_control *ct)
	{
	if (!try_module_get(ct->ops->owner))
	return -ENODEV;
	kref_get(&ct->ref);
	return 0;
	}
	EXPORT_SYMBOL_GPL(wf_get_control);

	void wf_put_control(struct wf_control *ct)
	{
	struct module *mod = ct->ops->owner;
	kref_put(&ct->ref, wf_control_release);
	module_put(mod);
	}
	EXPORT_SYMBOL_GPL(wf_put_control);


	/*
	* Sensors
	*/


	static void wf_sensor_release(struct kref *kref)
	{
	struct wf_sensor *sr = container_of(kref, struct wf_sensor, ref);

	DBG("wf: Deleting sensor %s\n", sr->name);

	if (sr->ops && sr->ops->release)
	sr->ops->release(sr);
	else
	kfree(sr);
	}

	static ssize_t wf_show_sensor(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct wf_sensor *sens = container_of(attr, struct wf_sensor, attr);
	s32 val = 0;
	int err;

	err = sens->ops->get_value(sens, &val);
	if (err < 0)
	return err;
	return sprintf(buf, "%d.%03d\n", FIX32TOPRINT(val));
	}

	int wf_register_sensor(struct wf_sensor *new_sr)
	{
	struct wf_sensor *sr;

	mutex_lock(&wf_lock);
	list_for_each_entry(sr, &wf_sensors, link) {
	if (!strcmp(sr->name, new_sr->name)) {
	printk(KERN_WARNING "windfarm: trying to register"
	" duplicate sensor %s\n", sr->name);
	mutex_unlock(&wf_lock);
	return -EEXIST;
	}
	}
	kref_init(&new_sr->ref);
	list_add(&new_sr->link, &wf_sensors);

	sysfs_attr_init(&new_sr->attr.attr);
	new_sr->attr.attr.name = new_sr->name;
	new_sr->attr.attr.mode = 0444;
	new_sr->attr.show = wf_show_sensor;
	new_sr->attr.store = NULL;
	if (device_create_file(&wf_platform_device.dev, &new_sr->attr))
	printk(KERN_WARNING "windfarm: device_create_file failed"
	" for %s\n", new_sr->name);
	/* the subsystem still does useful work without the file */

	DBG("wf: Registered sensor %s\n", new_sr->name);

	wf_notify(WF_EVENT_NEW_SENSOR, new_sr);
	mutex_unlock(&wf_lock);

	return 0;
	}
	EXPORT_SYMBOL_GPL(wf_register_sensor);

	void wf_unregister_sensor(struct wf_sensor *sr)
	{
	mutex_lock(&wf_lock);
	list_del(&sr->link);
	mutex_unlock(&wf_lock);

	DBG("wf: Unregistered sensor %s\n", sr->name);

	wf_put_sensor(sr);
	}
	EXPORT_SYMBOL_GPL(wf_unregister_sensor);

	int wf_get_sensor(struct wf_sensor *sr)
	{
	if (!try_module_get(sr->ops->owner))
	return -ENODEV;
	kref_get(&sr->ref);
	return 0;
	}
	EXPORT_SYMBOL_GPL(wf_get_sensor);

	void wf_put_sensor(struct wf_sensor *sr)
	{
	struct module *mod = sr->ops->owner;
	kref_put(&sr->ref, wf_sensor_release);
	module_put(mod);
	}
	EXPORT_SYMBOL_GPL(wf_put_sensor);


	/*
	* Client & notification
	*/

	int wf_register_client(struct notifier_block *nb)
	{
	int rc;
	struct wf_control *ct;
	struct wf_sensor *sr;

	mutex_lock(&wf_lock);
	rc = blocking_notifier_chain_register(&wf_client_list, nb);
	if (rc != 0)
	goto bail;
	wf_client_count++;
	list_for_each_entry(ct, &wf_controls, link)
	wf_notify(WF_EVENT_NEW_CONTROL, ct);
	list_for_each_entry(sr, &wf_sensors, link)
	wf_notify(WF_EVENT_NEW_SENSOR, sr);
	if (wf_client_count == 1)
	wf_start_thread();
	bail:
	mutex_unlock(&wf_lock);
	return rc;
	}
	EXPORT_SYMBOL_GPL(wf_register_client);

	int wf_unregister_client(struct notifier_block *nb)
	{
	mutex_lock(&wf_lock);
	blocking_notifier_chain_unregister(&wf_client_list, nb);
	wf_client_count--;
	if (wf_client_count == 0)
	wf_stop_thread();
	mutex_unlock(&wf_lock);

	return 0;
	}
	EXPORT_SYMBOL_GPL(wf_unregister_client);

	void wf_set_overtemp(void)
	{
	mutex_lock(&wf_lock);
	wf_overtemp++;
	if (wf_overtemp == 1) {
	printk(KERN_WARNING "windfarm: Overtemp condition detected !\n");
	wf_overtemp_counter = 0;
	wf_notify(WF_EVENT_OVERTEMP, NULL);
	}
	mutex_unlock(&wf_lock);
	}
	EXPORT_SYMBOL_GPL(wf_set_overtemp);

	void wf_clear_overtemp(void)
	{
	mutex_lock(&wf_lock);
	WARN_ON(wf_overtemp == 0);
	if (wf_overtemp == 0) {
	mutex_unlock(&wf_lock);
	return;
	}
	wf_overtemp--;
	if (wf_overtemp == 0) {
	printk(KERN_WARNING "windfarm: Overtemp condition cleared !\n");
	wf_notify(WF_EVENT_NORMALTEMP, NULL);
	}
	mutex_unlock(&wf_lock);
	}
	EXPORT_SYMBOL_GPL(wf_clear_overtemp);

	static int __init windfarm_core_init(void)
	{
	DBG("wf: core loaded\n");

	platform_device_register(&wf_platform_device);
	return 0;
	}

	static void __exit windfarm_core_exit(void)
	{
	BUG_ON(wf_client_count != 0);

	DBG("wf: core unloaded\n");

	platform_device_unregister(&wf_platform_device);
	}


	module_init(windfarm_core_init);
	module_exit(windfarm_core_exit);

	MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
	MODULE_DESCRIPTION("Core component of PowerMac thermal control");
	MODULE_LICENSE("GPL");