thermal: core: export apis to get slope and offset

Add apis for platform thermal drivers to query for slope and offset
attributes, which might be needed for temperature calculations.

Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index ee517be..707d735 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -435,6 +435,8 @@
 void thermal_cooling_device_unregister(struct thermal_cooling_device *);
 struct thermal_zone_device *thermal_zone_get_zone_by_name(const char *name);
 int thermal_zone_get_temp(struct thermal_zone_device *tz, int *temp);
+int thermal_zone_get_slope(struct thermal_zone_device *tz);
+int thermal_zone_get_offset(struct thermal_zone_device *tz);
 
 int get_tz_trend(struct thermal_zone_device *, int);
 struct thermal_instance *get_thermal_instance(struct thermal_zone_device *,
@@ -492,6 +494,12 @@
 static inline int thermal_zone_get_temp(
 		struct thermal_zone_device *tz, int *temp)
 { return -ENODEV; }
+static inline int thermal_zone_get_slope(
+		struct thermal_zone_device *tz)
+{ return -ENODEV; }
+static inline int thermal_zone_get_offset(
+		struct thermal_zone_device *tz)
+{ return -ENODEV; }
 static inline int get_tz_trend(struct thermal_zone_device *tz, int trip)
 { return -ENODEV; }
 static inline struct thermal_instance *