Thermal: Add Hysteresis attributes

The Linux Thermal Framework does not support hysteresis
attributes. Most thermal sensors, today, have a
hysteresis value associated with trip points.

This patch adds hysteresis attributes on a per-trip-point
basis, to the Thermal Framework. These attributes are
optionally writable.

Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index 6eaf914..cfc8d90 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -60,6 +60,10 @@
 			      unsigned long *);
 	int (*set_trip_temp) (struct thermal_zone_device *, int,
 			      unsigned long);
+	int (*get_trip_hyst) (struct thermal_zone_device *, int,
+			      unsigned long *);
+	int (*set_trip_hyst) (struct thermal_zone_device *, int,
+			      unsigned long);
 	int (*get_crit_temp) (struct thermal_zone_device *, unsigned long *);
 	int (*notify) (struct thermal_zone_device *, int,
 		       enum thermal_trip_type);
@@ -98,6 +102,7 @@
 	struct device device;
 	struct thermal_attr *trip_temp_attrs;
 	struct thermal_attr *trip_type_attrs;
+	struct thermal_attr *trip_hyst_attrs;
 	void *devdata;
 	int trips;
 	int tc1;