RE: [PATCH 2/8] Thermal: Create zone level APIs

["R, Durgadoss" <durgadoss.r@intel.com>]

> -----Original Message-----
> From: linux-pm-owner@vger.kernel.org [mailto:linux-pm-
> owner@vger.kernel.org] On Behalf Of Eduardo Valentin
> Sent: Friday, March 01, 2013 1:00 AM
> To: R, Durgadoss
> Cc: Zhang, Rui; linux-pm@vger.kernel.org; linux-kernel@vger.kernel.org;
> hongbo.zhang@linaro.org; wni@nvidia.com
> Subject: Re: [PATCH 2/8] Thermal: Create zone level APIs
> 
> On 05-02-2013 06:46, Durgadoss R wrote:
> > This patch adds a new thermal_zone structure to
> > thermal.h. Also, adds zone level APIs to the thermal
> > framework.
> >
> > A thermal zone is a hot spot on the platform, which
> > can have one or more sensors and cooling devices attached
> > to it. These sensors can be mapped to a set of cooling
> > devices, which when throttled, can help to bring down
> > the temperature of the hot spot.
> >
> > Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
> > ---
> >   drivers/thermal/thermal_sys.c |  196
> +++++++++++++++++++++++++++++++++++++++++
> >   include/linux/thermal.h       |   22 +++++
> >   2 files changed, 218 insertions(+)
> >
> > diff --git a/drivers/thermal/thermal_sys.c b/drivers/thermal/thermal_sys.c
> > index cb94497..838d4fb 100644
> > --- a/drivers/thermal/thermal_sys.c
> > +++ b/drivers/thermal/thermal_sys.c
> > @@ -43,19 +43,46 @@ MODULE_DESCRIPTION("Generic thermal
> management sysfs support");
> >   MODULE_LICENSE("GPL");
> >
> >   static DEFINE_IDR(thermal_tz_idr);
> > +static DEFINE_IDR(thermal_zone_idr);
> >   static DEFINE_IDR(thermal_cdev_idr);
> >   static DEFINE_IDR(thermal_sensor_idr);
> >   static DEFINE_MUTEX(thermal_idr_lock);
> >
> >   static LIST_HEAD(thermal_tz_list);
> >   static LIST_HEAD(thermal_sensor_list);
> > +static LIST_HEAD(thermal_zone_list);
> >   static LIST_HEAD(thermal_cdev_list);
> >   static LIST_HEAD(thermal_governor_list);
> >
> >   static DEFINE_MUTEX(thermal_list_lock);
> >   static DEFINE_MUTEX(sensor_list_lock);
> > +static DEFINE_MUTEX(zone_list_lock);
> >   static DEFINE_MUTEX(thermal_governor_lock);
> >
> > +#define for_each_thermal_sensor(pos) \
> > +	list_for_each_entry(pos, &thermal_sensor_list, node)
> > +
> > +#define for_each_thermal_zone(pos) \
> > +	list_for_each_entry(pos, &thermal_zone_list, node)
> > +
> > +#define GET_INDEX(tz, ptr, type)			\
> 
> Why do you need type? You seam to be using it only for sensors. It
> becomes a bit cryptic :-)

In the next patch, we use it for cooling devices also.

> 
> > +({							\
> > +	int i, ret = -EINVAL;				\
> > +	do {						\
> > +		if (!tz || !ptr)			\
> > +			break;				\
> > +		mutex_lock(&type##_list_lock);		\
> > +		for (i = 0; i < tz->type##_indx; i++) {	\
> > +			if (tz->type##s[i] == ptr) {	\
> > +				ret = i;		\
> > +				break;			\
> > +			}				\
> > +		}					\
> > +		mutex_unlock(&type##_list_lock);	\
> > +	} while (0);					\
> > +	ret;						\
> > +})
> > +
> >   static struct thermal_governor *__find_governor(const char *name)
> >   {
> >   	struct thermal_governor *pos;
> > @@ -421,15 +448,44 @@ static void thermal_zone_device_check(struct
> work_struct *work)
> >   	thermal_zone_device_update(tz);
> >   }
> >
> > +static void remove_sensor_from_zone(struct thermal_zone *tz,
> > +				struct thermal_sensor *ts)
> > +{
> > +	int j, indx;
> > +
> > +	indx = GET_INDEX(tz, ts, sensor);
> > +	if (indx < 0)
> > +		return;
> > +
> > +	sysfs_remove_link(&tz->device.kobj, kobject_name(&ts-
> >device.kobj));
> > +
> > +	/* Shift the entries in the tz->sensors array */
> > +	for (j = indx; j < MAX_SENSORS_PER_ZONE - 1; j++)
> > +		tz->sensors[j] = tz->sensors[j + 1];
> > +
> > +	tz->sensor_indx--;
> > +}
> > +
> >   /* sys I/F for thermal zone */
> >
> >   #define to_thermal_zone(_dev) \
> >   	container_of(_dev, struct thermal_zone_device, device)
> >
> > +#define to_zone(_dev) \
> > +	container_of(_dev, struct thermal_zone, device)
> > +
> >   #define to_thermal_sensor(_dev) \
> >   	container_of(_dev, struct thermal_sensor, device)
> >
> >   static ssize_t
> > +zone_name_show(struct device *dev, struct device_attribute *attr, char
> *buf)
> > +{
> > +	struct thermal_zone *tz = to_zone(dev);
> > +
> > +	return sprintf(buf, "%s\n", tz->name);
> snprintf
> 
> > +}
> > +
> > +static ssize_t
> >   sensor_name_show(struct device *dev, struct device_attribute *attr,
> char *buf)
> >   {
> >   	struct thermal_sensor *ts = to_thermal_sensor(dev);
> > @@ -811,6 +867,8 @@ static DEVICE_ATTR(policy, S_IRUGO | S_IWUSR,
> policy_show, policy_store);
> >   static DEVICE_ATTR(sensor_name, 0444, sensor_name_show, NULL);
> >   static DEVICE_ATTR(temp_input, 0444, sensor_temp_show, NULL);
> >
> > +static DEVICE_ATTR(zone_name, 0444, zone_name_show, NULL);
> > +
> >   /* sys I/F for cooling device */
> >   #define to_cooling_device(_dev)	\
> >   	container_of(_dev, struct thermal_cooling_device, device)
> > @@ -1656,6 +1714,136 @@ static int enable_sensor_thresholds(struct
> thermal_sensor *ts, int count)
> >   	return 0;
> >   }
> >
> > +struct thermal_zone *create_thermal_zone(const char *name, void
> *devdata)
> > +{
> > +	struct thermal_zone *tz;
> > +	int ret;
> > +
> > +	if (!name || (name && strlen(name) >= THERMAL_NAME_LENGTH))
> > +		return ERR_PTR(-EINVAL);
> > +
> > +	tz = kzalloc(sizeof(*tz), GFP_KERNEL);
> 
> devm_ helpers
> 
> > +	if (!tz)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	idr_init(&tz->idr);
> > +	ret = get_idr(&thermal_zone_idr, &thermal_idr_lock, &tz->id);
> > +	if (ret)
> > +		goto exit_free;
> > +
> > +	strcpy(tz->name, name);
> 
> strlcpy
> 
> > +	tz->devdata = devdata;
> > +	tz->device.class = &thermal_class;
> > +
> > +	dev_set_name(&tz->device, "zone%d", tz->id);
> > +	ret = device_register(&tz->device);
> > +	if (ret)
> > +		goto exit_idr;
> > +
> > +	ret = device_create_file(&tz->device, &dev_attr_zone_name);
> > +	if (ret)
> > +		goto exit_unregister;
> > +
> > +	/* Add this zone to the global list of thermal zones */
> > +	mutex_lock(&zone_list_lock);
> > +	list_add_tail(&tz->node, &thermal_zone_list);
> > +	mutex_unlock(&zone_list_lock);
> > +	return tz;
> > +
> > +exit_unregister:
> > +	device_unregister(&tz->device);
> > +exit_idr:
> > +	release_idr(&thermal_zone_idr, &thermal_idr_lock, tz->id);
> > +exit_free:
> > +	kfree(tz);
> > +	return ERR_PTR(ret);
> > +}
> > +EXPORT_SYMBOL(create_thermal_zone);
> > +
> > +void remove_thermal_zone(struct thermal_zone *tz)
> > +{
> > +	struct thermal_zone *pos, *next;
> > +	bool found = false;
> > +
> > +	if (!tz)
> > +		return;
> > +
> > +	mutex_lock(&zone_list_lock);
> > +
> > +	list_for_each_entry_safe(pos, next, &thermal_zone_list, node) {
> > +		if (pos == tz) {
> > +			list_del(&tz->node);
> > +			found = true;
> > +			break;
> > +		}
> > +	}
> > +
> > +	if (!found)
> > +		goto exit;
> > +
> > +	device_remove_file(&tz->device, &dev_attr_zone_name);
> > +
> > +	release_idr(&thermal_zone_idr, &thermal_idr_lock, tz->id);
> > +	idr_destroy(&tz->idr);
> > +
> > +	device_unregister(&tz->device);
> > +	kfree(tz);
> > +exit:
> > +	mutex_unlock(&zone_list_lock);
> > +	return;
> > +}
> > +EXPORT_SYMBOL(remove_thermal_zone);
> 
> Do we need to impose removal ordering here? Meaning, what happens if
> the
> above is called with sensors registered?

A zone only contains a symbolic link to a sensor. So, when this is called with
sensors registered, all the symbolic links will go away i.e /sys/../zone/sensorX
will go but /sys/../sensorX will remain as such.

> 
> > +
> > +struct thermal_sensor *get_sensor_by_name(const char *name)
> Why do you need this function? does not seam to be used anywhere in this
> patch. Besides it is unrelated to what this patch proposes itself to do.
> 
> > +{
> > +	struct thermal_sensor *pos;
> > +	struct thermal_sensor *ts = NULL;
> > +
> > +	mutex_lock(&sensor_list_lock);
> > +	for_each_thermal_sensor(pos) {
> > +		if (!strnicmp(pos->name, name, THERMAL_NAME_LENGTH))
> {
> > +			ts = pos;
> > +			break;
> > +		}
> > +	}
> > +	mutex_unlock(&sensor_list_lock);
> > +	return ts;
> > +}
> > +EXPORT_SYMBOL(get_sensor_by_name);
> > +
> > +int add_sensor_to_zone(struct thermal_zone *tz, struct thermal_sensor
> *ts)
> > +{
> > +	int ret;
> > +
> > +	if (!tz || !ts)
> > +		return -EINVAL;
> > +
> > +	mutex_lock(&zone_list_lock);
> > +
> > +	/* Ensure we are not adding the same sensor again!! */
> > +	ret = GET_INDEX(tz, ts, sensor);
> > +	if (ret >= 0) {
> > +		ret = -EEXIST;
> > +		goto exit_zone;
> > +	}
> > +
> > +	mutex_lock(&sensor_list_lock);
> > +
> > +	ret = sysfs_create_link(&tz->device.kobj, &ts->device.kobj,
> > +				kobject_name(&ts->device.kobj));
> > +	if (ret)
> > +		goto exit_sensor;
> > +
> > +	tz->sensors[tz->sensor_indx++] = ts;
> 
> you may overflow your sensors buffer with the above implementation.

Will add a check before the increment.

> 
> you may have a contention on sensors/sensor_indx.
> 
> Consider using linked lists.
> 
> > +
> > +exit_sensor:
> > +	mutex_unlock(&sensor_list_lock);
> > +exit_zone:
> > +	mutex_unlock(&zone_list_lock);
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL(add_sensor_to_zone);
> > +
> >   /**
> >    * thermal_sensor_register - register a new thermal sensor
> >    * @name:	name of the thermal sensor
> > @@ -1732,6 +1920,7 @@ EXPORT_SYMBOL(thermal_sensor_register);
> >   void thermal_sensor_unregister(struct thermal_sensor *ts)
> >   {
> >   	int i;
> > +	struct thermal_zone *tz;
> >   	struct thermal_sensor *pos, *next;
> >   	bool found = false;
> >
> > @@ -1751,6 +1940,13 @@ void thermal_sensor_unregister(struct
> thermal_sensor *ts)
> >   	if (!found)
> >   		return;
> >
> > +	mutex_lock(&zone_list_lock);
> > +
> > +	for_each_thermal_zone(tz)
> > +		remove_sensor_from_zone(tz, ts);
> > +
> > +	mutex_unlock(&zone_list_lock);
> > +
> >   	for (i = 0; i < ts->thresholds; i++) {
> >   		device_remove_file(&ts->device, &ts->thresh_attrs[i].attr);
> >   		if (ts->ops->get_hyst) {
> > diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> > index 5470dae..2194519 100644
> > --- a/include/linux/thermal.h
> > +++ b/include/linux/thermal.h
> > @@ -55,6 +55,8 @@
> >   #define DEFAULT_THERMAL_GOVERNOR       "user_space"
> >   #endif
> >
> > +#define MAX_SENSORS_PER_ZONE		5
> 
> 
> Why not making it a linked list? Why does it need to be static? Just
> trying to avoid to maintain this number sane, as we cannot predict what
> happens in future :-)

As I said earlier, making it a list makes things even more complex.
But I wanted this to be configurable through Kconfig, for which I
submitted a patch in my v2. But we had some comments against it.
So, we removed it, and need to revisit this later.

Thanks,
Durga

> 
> > +
> >   struct thermal_sensor;
> >   struct thermal_zone_device;
> >   struct thermal_cooling_device;
> > @@ -202,6 +204,21 @@ struct thermal_zone_device {
> >   	struct delayed_work poll_queue;
> >   };
> >
> > +struct thermal_zone {
> > +	char name[THERMAL_NAME_LENGTH];
> > +	int id;
> > +	void *devdata;
> > +	struct thermal_zone *ops;
> > +	struct thermal_governor *governor;
> > +	struct idr idr;
> > +	struct device device;
> > +	struct list_head node;
> > +
> > +	/* Sensor level information */
> > +	int sensor_indx; /* index into 'sensors' array */
> > +	struct thermal_sensor *sensors[MAX_SENSORS_PER_ZONE];
> > +};
> 
> 
> Could you please add documentation for the above structure? Why it does
> not need locking? what is *ops?
> > +
> >   /* Structure that holds thermal governor information */
> >   struct thermal_governor {
> >   	char name[THERMAL_NAME_LENGTH];
> > @@ -274,6 +291,11 @@ struct thermal_sensor
> *thermal_sensor_register(const char *, int,
> >   				struct thermal_sensor_ops *, void *);
> >   void thermal_sensor_unregister(struct thermal_sensor *);
> >
> > +struct thermal_zone *create_thermal_zone(const char *, void *);
> > +void remove_thermal_zone(struct thermal_zone *);
> > +int add_sensor_to_zone(struct thermal_zone *, struct thermal_sensor
> *);
> > +struct thermal_sensor *get_sensor_by_name(const char *);
> > +
> 
> I believe we need a better naming for this API. First suggestion is to
> use same prefix on all of them. Probably this comment applies not only
> to this specific patch.
> 
> Besides, for all functions above, you may want to add comments
> documenting them and their parameters?
> 
> >   #ifdef CONFIG_NET
> >   extern int thermal_generate_netlink_event(struct thermal_zone_device
> *tz,
> >   						enum events event);
> >
> 
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