linux-kernel - [PATCH v2 18/18] bitops: Add parity() macro for automatic type-based selection

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Message-Id: <20250301142409.2513835-19-visitorckw@gmail.com>
Date: Sat,  1 Mar 2025 22:24:09 +0800
From: Kuan-Wei Chiu <visitorckw@...il.com>
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	Kuan-Wei Chiu <visitorckw@...il.com>,
	Yu-Chun Lin <eleanor15x@...il.com>
Subject: [PATCH v2 18/18] bitops: Add parity() macro for automatic type-based selection

Introduce the parity() macro, which selects the appropriate parity
function (parity8(), parity16(), parity32(), or parity64()) based on
the size of the input type. This improves usability by allowing a
generic parity calculation without requiring explicit function
selection.

If the input type does not match the supported sizes, BUILD_BUG() is
triggered to catch invalid usage at compile time.

Co-developed-by: Yu-Chun Lin <eleanor15x@...il.com>
Signed-off-by: Yu-Chun Lin <eleanor15x@...il.com>
Signed-off-by: Kuan-Wei Chiu <visitorckw@...il.com>
---
Place this patch last in the series to avoid compilation errors.

 include/linux/bitops.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 41e9e7fb894b..fa4e45741dff 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -339,6 +339,28 @@ static inline __attribute_const__ int parity64(u64 val)
 	return __builtin_constant_p(val) ? _parity_const(val) : _parity64(val);
 }
 
+#define parity(val)			\
+({					\
+	int __ret;			\
+	switch (BITS_PER_TYPE(val)) {	\
+	case 64:			\
+		__ret = parity64(val);	\
+		break;			\
+	case 32:			\
+		__ret = parity32(val);	\
+		break;			\
+	case 16:			\
+		__ret = parity16(val);	\
+		break;			\
+	case 8:				\
+		__ret = parity8(val);	\
+		break;			\
+	default:			\
+		BUILD_BUG();		\
+	}				\
+	__ret;				\
+})
+
 /**
  * __ffs64 - find first set bit in a 64 bit word
  * @word: The 64 bit word
-- 
2.34.1