[PATCH RFC 14/40] compat: math64: add abs_diff()

[Casey Connolly]

Add the abs_diff() macro, copied directly from Linux 6.18.

Signed-off-by: Casey Connolly <casey.connolly at linaro.org>
---
 include/linux/math64.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/include/linux/math64.h b/include/linux/math64.h
index eaa9fd5b9685..70a7ee3ff1d3 100644
--- a/include/linux/math64.h
+++ b/include/linux/math64.h
@@ -256,5 +256,24 @@ static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 divisor)
 	return rl.ll;
 }
 #endif /* mul_u64_u32_div */
 
+/**
+ * abs_diff - return absolute value of the difference between the arguments
+ * @a: the first argument
+ * @b: the second argument
+ *
+ * @a and @b have to be of the same type. With this restriction we compare
+ * signed to signed and unsigned to unsigned. The result is the subtraction
+ * the smaller of the two from the bigger, hence result is always a positive
+ * value.
+ *
+ * Return: an absolute value of the difference between the @a and @b.
+ */
+#define abs_diff(a, b) ({			\
+	typeof(a) __a = (a);			\
+	typeof(b) __b = (b);			\
+	(void)(&__a == &__b);			\
+	__a > __b ? (__a - __b) : (__b - __a);	\
+})
+
 #endif /* _LINUX_MATH64_H */

-- 
2.51.0