linux-kernel - [v2 01/10] utils_macro: introduce find_closest

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Message-Id: <20211028101840.24632-2-andrea.merello@gmail.com>
Date:   Thu, 28 Oct 2021 12:18:31 +0200
From:   Andrea Merello <andrea.merello@...il.com>
To:     jic23@...nel.org, mchehab+huawei@...nel.org,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Cc:     lars@...afoo.de, robh+dt@...nel.org, andy.shevchenko@...il.com,
        matt.ranostay@...sulko.com, ardeleanalex@...il.com,
        jacopo@...ndi.org, Andrea Merello <andrea.merello@...il.com>,
        Andrea Merello <andrea.merello@....it>
Subject: [v2 01/10] utils_macro: introduce find_closest_unsorted()

This is similar to find_closest() and find_closest_descending(), but, it
doesn't make any assumption about the array being ordered.

Signed-off-by: Andrea Merello <andrea.merello@....it>
---
 include/linux/util_macros.h | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/include/linux/util_macros.h b/include/linux/util_macros.h
index 72299f261b25..b48f80ceb380 100644
--- a/include/linux/util_macros.h
+++ b/include/linux/util_macros.h
@@ -2,6 +2,8 @@
 #ifndef _LINUX_HELPER_MACROS_H_
 #define _LINUX_HELPER_MACROS_H_
 
+#include <linux/math.h>
+
 #define __find_closest(x, a, as, op)					\
 ({									\
 	typeof(as) __fc_i, __fc_as = (as) - 1;				\
@@ -38,4 +40,28 @@
  */
 #define find_closest_descending(x, a, as) __find_closest(x, a, as, >=)
 
+/**
+ * find_closest_unsorted - locate the closest element in a unsorted array
+ * @x: The reference value.
+ * @a: The array in which to look for the closest element.
+ * @as: Size of 'a'.
+ *
+ * Similar to find_closest() but 'a' has no requirement to being sorted
+ */
+#define find_closest_unsorted(x, a, as)					\
+({									\
+	typeof(x) __fc_best_delta, __fc_delta;				\
+	typeof(as) __fc_i, __fc_best_idx;				\
+	bool __fc_first = true;						\
+	for (__fc_i = 0; __fc_i < (as); __fc_i++) {			\
+		__fc_delta = abs(a[__fc_i] - (x));			\
+		if (__fc_first || __fc_delta < __fc_best_delta) {	\
+			__fc_best_delta = __fc_delta;			\
+			__fc_best_idx = __fc_i;				\
+		}							\
+		__fc_first = false;					\
+	}								\
+	(__fc_best_idx);						\
+})
+
 #endif
-- 
2.17.1