diff --git a/can-calc-bit-timing.c b/can-calc-bit-timing.c
index 0293b45..96f35f3 100644
--- a/can-calc-bit-timing.c
+++ b/can-calc-bit-timing.c
@@ -28,70 +28,38 @@
 #include <linux/types.h>
 #include <linux/can/netlink.h>
 
-/* imported from kernel */
+/* seems not to be defined in errno.h */
+#ifndef ENOTSUPP
+#define ENOTSUPP	524	/* Operation is not supported */
+#endif
 
-/**
- * abs - return absolute value of an argument
- * @x: the value.  If it is unsigned type, it is converted to signed type first.
- *     char is treated as if it was signed (regardless of whether it really is)
- *     but the macro's return type is preserved as char.
- *
- * Return: an absolute value of x.
- */
-#define abs(x)	__abs_choose_expr(x, long long,				\
-		__abs_choose_expr(x, long,				\
-		__abs_choose_expr(x, int,				\
-		__abs_choose_expr(x, short,				\
-		__abs_choose_expr(x, char,				\
-		__builtin_choose_expr(					\
-			__builtin_types_compatible_p(typeof(x), char),	\
-			(char)({ signed char __x = (x); __x<0?-__x:__x; }), \
-			((void)0)))))))
+/* useful defines */
+#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
 
-#define __abs_choose_expr(x, type, other) __builtin_choose_expr(	\
-	__builtin_types_compatible_p(typeof(x),   signed type) ||	\
-	__builtin_types_compatible_p(typeof(x), unsigned type),		\
-	({ signed type __x = (x); __x < 0 ? -__x : __x; }), other)
+#define do_div(a,b) a = (a) / (b)
 
-/*
- * min()/max()/clamp() macros that also do
- * strict type-checking.. See the
- * "unnecessary" pointer comparison.
- */
-#define min(x, y) ({				\
-	typeof(x) _min1 = (x);			\
-	typeof(y) _min2 = (y);			\
-	(void) (&_min1 == &_min2);		\
-	_min1 < _min2 ? _min1 : _min2; })
-
-#define max(x, y) ({				\
-	typeof(x) _max1 = (x);			\
-	typeof(y) _max2 = (y);			\
-	(void) (&_max1 == &_max2);		\
-	_max1 > _max2 ? _max1 : _max2; })
+#define abs(x) ({				\
+		long __x = (x);			\
+		(__x < 0) ? -__x : __x;		\
+	})
 
 /**
  * clamp - return a value clamped to a given range with strict typechecking
  * @val: current value
- * @lo: lowest allowable value
- * @hi: highest allowable value
+ * @min: minimum allowable value
+ * @max: maximum allowable value
  *
- * This macro does strict typechecking of lo/hi to make sure they are of the
+ * 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, lo, hi) min((typeof(val))max(val, lo), hi)
-
-# define do_div(n,base) ({					\
-	uint32_t __base = (base);				\
-	uint32_t __rem;						\
-	__rem = ((uint64_t)(n)) % __base;			\
-	(n) = ((uint64_t)(n)) / __base;				\
-	__rem;							\
- })
-
-/* */
-
-#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
+#define clamp(val, min, max) ({			\
+	typeof(val) __val = (val);		\
+	typeof(min) __min = (min);		\
+	typeof(max) __max = (max);		\
+	(void) (&__val == &__min);		\
+	(void) (&__val == &__max);		\
+	__val = __val < __min ? __min: __val;	\
+	__val > __max ? __max: __val; })
 
 /* we don't want to see these prints */
 #define netdev_err(dev, format, arg...) do { } while (0)