diff mbox series

[v4,01/30] thermal/core: Add a generic thermal_zone_get_trip() function

Message ID 20220921094244.606948-2-daniel.lezcano@linaro.org
State New
Headers show
Series Rework the trip points creation | expand

Commit Message

Daniel Lezcano Sept. 21, 2022, 9:42 a.m. UTC 
The thermal_zone_device_ops structure defines a set of ops family,
get_trip_temp(), get_trip_hyst(), get_trip_type(). Each of them is
returning a property of a trip point.

The result is the code is calling the ops everywhere to get a trip
point which is supposed to be defined in the backend driver. It is a
non-sense as a thermal trip can be generic and used by the backend
driver to declare its trip points.

Part of the thermal framework has been changed and all the OF thermal
drivers are using the same definition for the trip point and use a
thermal zone registration variant to pass those trip points which are
part of the thermal zone device structure.

Consequently, we can use a generic function to get the trip points
when they are stored in the thermal zone device structure.

This approach can be generalized to all the drivers and we can get rid
of the ops->get_trip_*. That will result to a much more simpler code
and make possible to rework how the thermal trip are handled in the
thermal core framework as discussed previously.

This change adds a function thermal_zone_get_trip() where we get the
thermal trip point structure which contains all the properties (type,
temp, hyst) instead of doing multiple calls to ops->get_trip_*.

That opens the door for trip point extension with more attributes. For
instance, replacing the trip points disabled bitmask with a 'disabled'
field in the structure.

Here we replace all the calls to ops->get_trip_* in the thermal core
code with a call to the thermal_zone_get_trip() function.

While at it, add the thermal_zone_get_num_trips() to encapsulate the
code more and reduce the grip with the thermal framework internals.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/thermal/thermal_core.c    | 87 +++++++++++++++++++++++--------
 drivers/thermal/thermal_helpers.c | 28 +++++-----
 drivers/thermal/thermal_netlink.c | 21 ++++----
 drivers/thermal/thermal_sysfs.c   | 66 +++++++++--------------
 include/linux/thermal.h           |  5 ++
 5 files changed, 118 insertions(+), 89 deletions(-)

Comments

Zhang, Rui Sept. 23, 2022, 1:54 p.m. UTC | #1 
> @@ -1142,6 +1138,52 @@ static void thermal_set_delay_jiffies(unsigned
> long *delay_jiffies, int delay_ms
>  		*delay_jiffies = round_jiffies(*delay_jiffies);
>  }
>  
> +int thermal_zone_get_num_trips(struct thermal_zone_device *tz)
> +{
> +	return tz->num_trips;
> +}
> +EXPORT_SYMBOL_GPL(thermal_zone_get_num_trips);
> +
> +static int __thermal_zone_get_trip(struct thermal_zone_device *tz,
> int trip_id,
> +				   struct thermal_trip *trip)
> +{
> +	int ret;
> +
> +	if (!tz || trip_id < 0 || trip_id >= tz->num_trips || !trip)
> +		return -EINVAL;
> +
> +	if (tz->trips) {
> +		*trip = tz->trips[trip_id];
> +		return 0;
> +	}
> +
> +	if (tz->ops->get_trip_hyst) {
> +		ret = tz->ops->get_trip_hyst(tz, trip_id, &trip-
> >hysteresis);
> +		if (ret)
> +			return ret;
> +	} else trip->hysteresis = 0;

a separate line?

Other than that,
Reviewed-by: Zhang Rui <rui.zhang@intel.com>

thanks,
rui
Marek Szyprowski Sept. 23, 2022, 10:19 p.m. UTC | #2 
Hi Daniel,

On 21.09.2022 11:42, Daniel Lezcano wrote:
> The thermal_zone_device_ops structure defines a set of ops family,
> get_trip_temp(), get_trip_hyst(), get_trip_type(). Each of them is
> returning a property of a trip point.
>
> The result is the code is calling the ops everywhere to get a trip
> point which is supposed to be defined in the backend driver. It is a
> non-sense as a thermal trip can be generic and used by the backend
> driver to declare its trip points.
>
> Part of the thermal framework has been changed and all the OF thermal
> drivers are using the same definition for the trip point and use a
> thermal zone registration variant to pass those trip points which are
> part of the thermal zone device structure.
>
> Consequently, we can use a generic function to get the trip points
> when they are stored in the thermal zone device structure.
>
> This approach can be generalized to all the drivers and we can get rid
> of the ops->get_trip_*. That will result to a much more simpler code
> and make possible to rework how the thermal trip are handled in the
> thermal core framework as discussed previously.
>
> This change adds a function thermal_zone_get_trip() where we get the
> thermal trip point structure which contains all the properties (type,
> temp, hyst) instead of doing multiple calls to ops->get_trip_*.
>
> That opens the door for trip point extension with more attributes. For
> instance, replacing the trip points disabled bitmask with a 'disabled'
> field in the structure.
>
> Here we replace all the calls to ops->get_trip_* in the thermal core
> code with a call to the thermal_zone_get_trip() function.
>
> While at it, add the thermal_zone_get_num_trips() to encapsulate the
> code more and reduce the grip with the thermal framework internals.
>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

This patch landed in linux next-20220923 as commit 78ffa3e58d93 
("thermal/core: Add a generic thermal_zone_get_trip() function"). 
Unfortunately it introduces a deadlock:

thermal_zone_device_update() calls handle_thermal_trip() under the 
tz->lock, which in turn calls thermal_zone_get_trip(), which gathers 
again tz->lock. I've tried to fix this by switching 
handle_thermal_trip() to call __thermal_zone_get_trip().

This helps for fixing the issue in this change, but then I've tried to 
apply it on top of linux next-20220923. Unfortunately it fails again. It 
looks that the other changes also assumes that calling 
thermal_zone_get_trip() is possible under the tz->lock, because in my 
case it turned out that handle_non_critical_trips() called 
step_wise_throttle(), which in turn called thermal_zone_get_trip(). I 
gave up fixing this. Please re-check possible call paths and adjust 
locking to them.


> ---
>   drivers/thermal/thermal_core.c    | 87 +++++++++++++++++++++++--------
>   drivers/thermal/thermal_helpers.c | 28 +++++-----
>   drivers/thermal/thermal_netlink.c | 21 ++++----
>   drivers/thermal/thermal_sysfs.c   | 66 +++++++++--------------
>   include/linux/thermal.h           |  5 ++
>   5 files changed, 118 insertions(+), 89 deletions(-)
>
> ...

Best regards
Daniel Lezcano Sept. 24, 2022, 5:46 p.m. UTC | #3 
On 24/09/2022 00:19, Marek Szyprowski wrote:
> Hi Daniel,
> 
> On 21.09.2022 11:42, Daniel Lezcano wrote:
>> The thermal_zone_device_ops structure defines a set of ops family,
>> get_trip_temp(), get_trip_hyst(), get_trip_type(). Each of them is
>> returning a property of a trip point.
>>
>> The result is the code is calling the ops everywhere to get a trip
>> point which is supposed to be defined in the backend driver. It is a
>> non-sense as a thermal trip can be generic and used by the backend
>> driver to declare its trip points.
>>
>> Part of the thermal framework has been changed and all the OF thermal
>> drivers are using the same definition for the trip point and use a
>> thermal zone registration variant to pass those trip points which are
>> part of the thermal zone device structure.
>>
>> Consequently, we can use a generic function to get the trip points
>> when they are stored in the thermal zone device structure.
>>
>> This approach can be generalized to all the drivers and we can get rid
>> of the ops->get_trip_*. That will result to a much more simpler code
>> and make possible to rework how the thermal trip are handled in the
>> thermal core framework as discussed previously.
>>
>> This change adds a function thermal_zone_get_trip() where we get the
>> thermal trip point structure which contains all the properties (type,
>> temp, hyst) instead of doing multiple calls to ops->get_trip_*.
>>
>> That opens the door for trip point extension with more attributes. For
>> instance, replacing the trip points disabled bitmask with a 'disabled'
>> field in the structure.
>>
>> Here we replace all the calls to ops->get_trip_* in the thermal core
>> code with a call to the thermal_zone_get_trip() function.
>>
>> While at it, add the thermal_zone_get_num_trips() to encapsulate the
>> code more and reduce the grip with the thermal framework internals.
>>
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
> 
> This patch landed in linux next-20220923 as commit 78ffa3e58d93
> ("thermal/core: Add a generic thermal_zone_get_trip() function").
> Unfortunately it introduces a deadlock:
> 
> thermal_zone_device_update() calls handle_thermal_trip() under the
> tz->lock, which in turn calls thermal_zone_get_trip(), which gathers
> again tz->lock. I've tried to fix this by switching
> handle_thermal_trip() to call __thermal_zone_get_trip().
> 
> This helps for fixing the issue in this change, but then I've tried to
> apply it on top of linux next-20220923. Unfortunately it fails again. It
> looks that the other changes also assumes that calling
> thermal_zone_get_trip() is possible under the tz->lock, because in my
> case it turned out that handle_non_critical_trips() called
> step_wise_throttle(), which in turn called thermal_zone_get_trip(). I
> gave up fixing this. Please re-check possible call paths and adjust
> locking to them.

Yes, you are correct. Those paths have the lock held. I'm fixing this
diff mbox series

Patch

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 99c0c19fa5a6..381d85ec74a0 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -341,35 +341,31 @@  static void handle_critical_trips(struct thermal_zone_device *tz,
 		tz->ops->critical(tz);
 }
 
-static void handle_thermal_trip(struct thermal_zone_device *tz, int trip)
+static void handle_thermal_trip(struct thermal_zone_device *tz, int trip_id)
 {
-	enum thermal_trip_type type;
-	int trip_temp, hyst = 0;
+	struct thermal_trip trip;
 
 	/* Ignore disabled trip points */
-	if (test_bit(trip, &tz->trips_disabled))
+	if (test_bit(trip_id, &tz->trips_disabled))
 		return;
 
-	tz->ops->get_trip_temp(tz, trip, &trip_temp);
-	tz->ops->get_trip_type(tz, trip, &type);
-	if (tz->ops->get_trip_hyst)
-		tz->ops->get_trip_hyst(tz, trip, &hyst);
+	thermal_zone_get_trip(tz, trip_id, &trip);
 
 	if (tz->last_temperature != THERMAL_TEMP_INVALID) {
-		if (tz->last_temperature < trip_temp &&
-		    tz->temperature >= trip_temp)
-			thermal_notify_tz_trip_up(tz->id, trip,
+		if (tz->last_temperature < trip.temperature &&
+		    tz->temperature >= trip.temperature)
+			thermal_notify_tz_trip_up(tz->id, trip_id,
 						  tz->temperature);
-		if (tz->last_temperature >= trip_temp &&
-		    tz->temperature < (trip_temp - hyst))
-			thermal_notify_tz_trip_down(tz->id, trip,
+		if (tz->last_temperature >= trip.temperature &&
+		    tz->temperature < (trip.temperature - trip.hysteresis))
+			thermal_notify_tz_trip_down(tz->id, trip_id,
 						    tz->temperature);
 	}
 
-	if (type == THERMAL_TRIP_CRITICAL || type == THERMAL_TRIP_HOT)
-		handle_critical_trips(tz, trip, trip_temp, type);
+	if (trip.type == THERMAL_TRIP_CRITICAL || trip.type == THERMAL_TRIP_HOT)
+		handle_critical_trips(tz, trip_id, trip.temperature, trip.type);
 	else
-		handle_non_critical_trips(tz, trip);
+		handle_non_critical_trips(tz, trip_id);
 }
 
 static void update_temperature(struct thermal_zone_device *tz)
@@ -1142,6 +1138,52 @@  static void thermal_set_delay_jiffies(unsigned long *delay_jiffies, int delay_ms
 		*delay_jiffies = round_jiffies(*delay_jiffies);
 }
 
+int thermal_zone_get_num_trips(struct thermal_zone_device *tz)
+{
+	return tz->num_trips;
+}
+EXPORT_SYMBOL_GPL(thermal_zone_get_num_trips);
+
+static int __thermal_zone_get_trip(struct thermal_zone_device *tz, int trip_id,
+				   struct thermal_trip *trip)
+{
+	int ret;
+
+	if (!tz || trip_id < 0 || trip_id >= tz->num_trips || !trip)
+		return -EINVAL;
+
+	if (tz->trips) {
+		*trip = tz->trips[trip_id];
+		return 0;
+	}
+
+	if (tz->ops->get_trip_hyst) {
+		ret = tz->ops->get_trip_hyst(tz, trip_id, &trip->hysteresis);
+		if (ret)
+			return ret;
+	} else trip->hysteresis = 0;
+
+	ret = tz->ops->get_trip_temp(tz, trip_id, &trip->temperature);
+	if (ret)
+		return ret;
+
+	return tz->ops->get_trip_type(tz, trip_id, &trip->type);
+}
+
+int thermal_zone_get_trip(struct thermal_zone_device *tz, int trip_id,
+			  struct thermal_trip *trip)
+{
+	int ret;
+
+	mutex_lock(&tz->lock);
+	ret = __thermal_zone_get_trip(tz, trip_id, trip);
+	mutex_unlock(&tz->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(thermal_zone_get_trip);
+
+
 /**
  * thermal_zone_device_register_with_trips() - register a new thermal zone device
  * @type:	the thermal zone device type
@@ -1174,8 +1216,6 @@  thermal_zone_device_register_with_trips(const char *type, struct thermal_trip *t
 					int polling_delay)
 {
 	struct thermal_zone_device *tz;
-	enum thermal_trip_type trip_type;
-	int trip_temp;
 	int id;
 	int result;
 	int count;
@@ -1202,7 +1242,7 @@  thermal_zone_device_register_with_trips(const char *type, struct thermal_trip *t
 		return ERR_PTR(-EINVAL);
 	}
 
-	if (num_trips > 0 && (!ops->get_trip_type || !ops->get_trip_temp))
+	if (num_trips > 0 && (!ops->get_trip_type || !ops->get_trip_temp) && !trips)
 		return ERR_PTR(-EINVAL);
 
 	tz = kzalloc(sizeof(*tz), GFP_KERNEL);
@@ -1252,9 +1292,10 @@  thermal_zone_device_register_with_trips(const char *type, struct thermal_trip *t
 		goto release_device;
 
 	for (count = 0; count < num_trips; count++) {
-		if (tz->ops->get_trip_type(tz, count, &trip_type) ||
-		    tz->ops->get_trip_temp(tz, count, &trip_temp) ||
-		    !trip_temp)
+		struct thermal_trip trip;
+
+		result = thermal_zone_get_trip(tz, count, &trip);
+		if (result)
 			set_bit(count, &tz->trips_disabled);
 	}
 
diff --git a/drivers/thermal/thermal_helpers.c b/drivers/thermal/thermal_helpers.c
index c65cdce8f856..e1264940136a 100644
--- a/drivers/thermal/thermal_helpers.c
+++ b/drivers/thermal/thermal_helpers.c
@@ -69,7 +69,7 @@  int __thermal_zone_get_temp(struct thermal_zone_device *tz, int *temp)
 	int ret = -EINVAL;
 	int count;
 	int crit_temp = INT_MAX;
-	enum thermal_trip_type type;
+	struct thermal_trip trip;
 
 	lockdep_assert_held(&tz->lock);
 
@@ -80,10 +80,9 @@  int __thermal_zone_get_temp(struct thermal_zone_device *tz, int *temp)
 
 	if (IS_ENABLED(CONFIG_THERMAL_EMULATION) && tz->emul_temperature) {
 		for (count = 0; count < tz->num_trips; count++) {
-			ret = tz->ops->get_trip_type(tz, count, &type);
-			if (!ret && type == THERMAL_TRIP_CRITICAL) {
-				ret = tz->ops->get_trip_temp(tz, count,
-						&crit_temp);
+			ret = thermal_zone_get_trip(tz, count, &trip);
+			if (!ret && trip.type == THERMAL_TRIP_CRITICAL) {
+				crit_temp = trip.temperature;
 				break;
 			}
 		}
@@ -124,29 +123,30 @@  EXPORT_SYMBOL_GPL(thermal_zone_get_temp);
 
 void __thermal_zone_set_trips(struct thermal_zone_device *tz)
 {
-	int low = -INT_MAX;
-	int high = INT_MAX;
-	int trip_temp, hysteresis;
+	struct thermal_trip trip;
+	int low = -INT_MAX, high = INT_MAX;
 	int i, ret;
 
 	lockdep_assert_held(&tz->lock);
 
-	if (!tz->ops->set_trips || !tz->ops->get_trip_hyst)
+	if (!tz->ops->set_trips)
 		return;
 
 	for (i = 0; i < tz->num_trips; i++) {
 		int trip_low;
 
-		tz->ops->get_trip_temp(tz, i, &trip_temp);
-		tz->ops->get_trip_hyst(tz, i, &hysteresis);
+		ret = thermal_zone_get_trip(tz, i , &trip);
+		if (ret)
+			return;
 
-		trip_low = trip_temp - hysteresis;
+		trip_low = trip.temperature - trip.hysteresis;
 
 		if (trip_low < tz->temperature && trip_low > low)
 			low = trip_low;
 
-		if (trip_temp > tz->temperature && trip_temp < high)
-			high = trip_temp;
+		if (trip.temperature > tz->temperature &&
+		    trip.temperature < high)
+			high = trip.temperature;
 	}
 
 	/* No need to change trip points */
diff --git a/drivers/thermal/thermal_netlink.c b/drivers/thermal/thermal_netlink.c
index 050d243a5fa1..ce56d441c88c 100644
--- a/drivers/thermal/thermal_netlink.c
+++ b/drivers/thermal/thermal_netlink.c
@@ -452,7 +452,8 @@  static int thermal_genl_cmd_tz_get_trip(struct param *p)
 	struct sk_buff *msg = p->msg;
 	struct thermal_zone_device *tz;
 	struct nlattr *start_trip;
-	int i, id;
+	struct thermal_trip trip;
+	int ret, i, id;
 
 	if (!p->attrs[THERMAL_GENL_ATTR_TZ_ID])
 		return -EINVAL;
@@ -471,18 +472,14 @@  static int thermal_genl_cmd_tz_get_trip(struct param *p)
 
 	for (i = 0; i < tz->num_trips; i++) {
 
-		enum thermal_trip_type type;
-		int temp, hyst = 0;
-
-		tz->ops->get_trip_type(tz, i, &type);
-		tz->ops->get_trip_temp(tz, i, &temp);
-		if (tz->ops->get_trip_hyst)
-			tz->ops->get_trip_hyst(tz, i, &hyst);
-
+		ret = thermal_zone_get_trip(tz, i, &trip);
+		if (ret)
+			goto out_cancel_nest;
+		
 		if (nla_put_u32(msg, THERMAL_GENL_ATTR_TZ_TRIP_ID, i) ||
-		    nla_put_u32(msg, THERMAL_GENL_ATTR_TZ_TRIP_TYPE, type) ||
-		    nla_put_u32(msg, THERMAL_GENL_ATTR_TZ_TRIP_TEMP, temp) ||
-		    nla_put_u32(msg, THERMAL_GENL_ATTR_TZ_TRIP_HYST, hyst))
+		    nla_put_u32(msg, THERMAL_GENL_ATTR_TZ_TRIP_TYPE, trip.type) ||
+		    nla_put_u32(msg, THERMAL_GENL_ATTR_TZ_TRIP_TEMP, trip.temperature) ||
+		    nla_put_u32(msg, THERMAL_GENL_ATTR_TZ_TRIP_HYST, trip.hysteresis))
 			goto out_cancel_nest;
 	}
 
diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
index 78c5841bdfae..75f6b151a58b 100644
--- a/drivers/thermal/thermal_sysfs.c
+++ b/drivers/thermal/thermal_sysfs.c
@@ -83,20 +83,17 @@  trip_point_type_show(struct device *dev, struct device_attribute *attr,
 		     char *buf)
 {
 	struct thermal_zone_device *tz = to_thermal_zone(dev);
-	enum thermal_trip_type type;
-	int trip, result;
+	struct thermal_trip trip;
+	int trip_id, result;
 
-	if (!tz->ops->get_trip_type)
-		return -EPERM;
-
-	if (sscanf(attr->attr.name, "trip_point_%d_type", &trip) != 1)
+	if (sscanf(attr->attr.name, "trip_point_%d_type", &trip_id) != 1)
 		return -EINVAL;
 
-	result = tz->ops->get_trip_type(tz, trip, &type);
+	result = thermal_zone_get_trip(tz, trip_id, &trip);
 	if (result)
 		return result;
 
-	switch (type) {
+	switch (trip.type) {
 	case THERMAL_TRIP_CRITICAL:
 		return sprintf(buf, "critical\n");
 	case THERMAL_TRIP_HOT:
@@ -115,37 +112,31 @@  trip_point_temp_store(struct device *dev, struct device_attribute *attr,
 		      const char *buf, size_t count)
 {
 	struct thermal_zone_device *tz = to_thermal_zone(dev);
-	int trip, ret;
-	int temperature, hyst = 0;
-	enum thermal_trip_type type;
+	struct thermal_trip trip;
+	int trip_id, ret;
 
 	if (!tz->ops->set_trip_temp && !tz->trips)
 		return -EPERM;
 
-	if (sscanf(attr->attr.name, "trip_point_%d_temp", &trip) != 1)
+	if (sscanf(attr->attr.name, "trip_point_%d_temp", &trip_id) != 1)
 		return -EINVAL;
 
-	if (kstrtoint(buf, 10, &temperature))
+	if (kstrtoint(buf, 10, &trip.temperature))
 		return -EINVAL;
 
-	ret = tz->ops->set_trip_temp(tz, trip, temperature);
+	ret = tz->ops->set_trip_temp(tz, trip_id, trip.temperature);
 	if (ret)
 		return ret;
 
 	if (tz->trips)
-		tz->trips[trip].temperature = temperature;
-
-	if (tz->ops->get_trip_hyst) {
-		ret = tz->ops->get_trip_hyst(tz, trip, &hyst);
-		if (ret)
-			return ret;
-	}
+		tz->trips[trip_id].temperature = trip.temperature;
 
-	ret = tz->ops->get_trip_type(tz, trip, &type);
+	ret = thermal_zone_get_trip(tz, trip_id, &trip);
 	if (ret)
 		return ret;
 
-	thermal_notify_tz_trip_change(tz->id, trip, type, temperature, hyst);
+	thermal_notify_tz_trip_change(tz->id, trip_id, trip.type,
+				      trip.temperature, trip.hysteresis);
 
 	thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
 
@@ -157,21 +148,17 @@  trip_point_temp_show(struct device *dev, struct device_attribute *attr,
 		     char *buf)
 {
 	struct thermal_zone_device *tz = to_thermal_zone(dev);
-	int trip, ret;
-	int temperature;
-
-	if (!tz->ops->get_trip_temp)
-		return -EPERM;
+	struct thermal_trip trip;
+	int trip_id, ret;
 
-	if (sscanf(attr->attr.name, "trip_point_%d_temp", &trip) != 1)
+	if (sscanf(attr->attr.name, "trip_point_%d_temp", &trip_id) != 1)
 		return -EINVAL;
 
-	ret = tz->ops->get_trip_temp(tz, trip, &temperature);
-
+	ret = thermal_zone_get_trip(tz, trip_id, &trip);
 	if (ret)
 		return ret;
 
-	return sprintf(buf, "%d\n", temperature);
+	return sprintf(buf, "%d\n", trip.temperature);
 }
 
 static ssize_t
@@ -209,18 +196,17 @@  trip_point_hyst_show(struct device *dev, struct device_attribute *attr,
 		     char *buf)
 {
 	struct thermal_zone_device *tz = to_thermal_zone(dev);
-	int trip, ret;
-	int temperature;
+	struct thermal_trip trip;
+	int trip_id, ret;
 
-	if (!tz->ops->get_trip_hyst)
-		return -EPERM;
-
-	if (sscanf(attr->attr.name, "trip_point_%d_hyst", &trip) != 1)
+	if (sscanf(attr->attr.name, "trip_point_%d_hyst", &trip_id) != 1)
 		return -EINVAL;
 
-	ret = tz->ops->get_trip_hyst(tz, trip, &temperature);
+	ret = thermal_zone_get_trip(tz, trip_id, &trip);
+	if (ret)
+		return ret;
 
-	return ret ? ret : sprintf(buf, "%d\n", temperature);
+	return ret ? ret : sprintf(buf, "%d\n", trip.hysteresis);
 }
 
 static ssize_t
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index a5a18351a898..09dc09228717 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -335,6 +335,11 @@  static inline void devm_thermal_of_zone_unregister(struct device *dev,
 }
 #endif
 
+int thermal_zone_get_trip(struct thermal_zone_device *tz, int trip_id,
+			  struct thermal_trip *trip);
+
+int thermal_zone_get_num_trips(struct thermal_zone_device *tz);
+
 #ifdef CONFIG_THERMAL
 struct thermal_zone_device *thermal_zone_device_register(const char *, int, int,
 		void *, struct thermal_zone_device_ops *,