add kerneldoc for clamp(), clamp_t(), clamp_val() macros

index c74460c..d57e537 100644
@@ -351,6 +351,15 @@ static inline int __attribute__ ((format (printf, 1, 2))) pr_debug(const char *
 	(void) (&_max1 == &_max2);		\
 	_max1 > _max2 ? _max1 : _max2; })
 
+/**
+ * clamp - return a value clamped to a given range with strict typechecking
+ * @val: current value
+ * @min: minimum allowable value
+ * @max: maximum allowable value
+ *
+ * This macro does strict typechecking of min/max to make sure they are of the
+ * same type as val.  See the unnecessary pointer comparisons.
+ */
 #define clamp(val, min, max) ({			\
 	typeof(val) __val = (val);		\
 	typeof(min) __min = (min);		\

@@ -376,6 +385,16 @@ static inline int __attribute__ ((format (printf, 1, 2))) pr_debug(const char *
 	type __max2 = (y);			\
 	__max1 > __max2 ? __max1: __max2; })
 
+/**
+ * clamp_t - return a value clamped to a given range using a given type
+ * @type: the type of variable to use
+ * @val: current value
+ * @min: minimum allowable value
+ * @max: maximum allowable value
+ *
+ * This macro does no typechecking and uses temporary variables of type
+ * 'type' to make all the comparisons.
+ */
 #define clamp_t(type, val, min, max) ({		\
 	type __val = (val);			\
 	type __min = (min);			\

@@ -383,6 +402,17 @@ static inline int __attribute__ ((format (printf, 1, 2))) pr_debug(const char *
 	__val = __val < __min ? __min: __val;	\
 	__val > __max ? __max: __val; })
 
+/**
+ * clamp_val - return a value clamped to a given range using val's type
+ * @val: current value
+ * @min: minimum allowable value
+ * @max: maximum allowable value
+ *
+ * This macro does no typechecking and uses temporary variables of whatever
+ * type the input argument 'val' is.  This is useful when val is an unsigned
+ * type and min and max are literals that will otherwise be assigned a signed
+ * integer type.
+ */
 #define clamp_val(val, min, max) ({		\
 	typeof(val) __val = (val);		\
 	typeof(val) __min = (min);		\