[PATCH 01/31] bitops: add parity functions

[Zhaoxiu Zeng]

From: Zeng Zhaoxiu <zhaoxiu.zeng@xxxxxxxxx>

When I do "grep parity -r linux", I found many parity calculations distributed in many drivers.
These patches provide generic and architecture-specific parity calculations.

Signed-off-by: Zeng Zhaoxiu <zhaoxiu.zeng@xxxxxxxxx>
---
 include/asm-generic/bitops.h              |  1 +
 include/asm-generic/bitops/arch_parity.h  | 39 +++++++++++++++++++++++++++++++
 include/asm-generic/bitops/const_parity.h | 36 ++++++++++++++++++++++++++++
 include/asm-generic/bitops/parity.h       |  7 ++++++
 include/linux/bitops.h                    |  5 ++++
 5 files changed, 88 insertions(+)
 create mode 100644 include/asm-generic/bitops/arch_parity.h
 create mode 100644 include/asm-generic/bitops/const_parity.h
 create mode 100644 include/asm-generic/bitops/parity.h

diff --git a/include/asm-generic/bitops.h b/include/asm-generic/bitops.h
index dcdcacf..d85722f 100644
--- a/include/asm-generic/bitops.h
+++ b/include/asm-generic/bitops.h
@@ -27,6 +27,7 @@
 #include <asm-generic/bitops/sched.h>
 #include <asm-generic/bitops/ffs.h>
 #include <asm-generic/bitops/hweight.h>
+#include <asm-generic/bitops/parity.h>
 #include <asm-generic/bitops/lock.h>
 
 #include <asm-generic/bitops/atomic.h>
diff --git a/include/asm-generic/bitops/arch_parity.h b/include/asm-generic/bitops/arch_parity.h
new file mode 100644
index 0000000..8d51eb3
--- /dev/null
+++ b/include/asm-generic/bitops/arch_parity.h
@@ -0,0 +1,39 @@
+#ifndef _ASM_GENERIC_BITOPS_ARCH_PARITY_H_
+#define _ASM_GENERIC_BITOPS_ARCH_PARITY_H_
+
+#include <asm/types.h>
+
+/*
+ * Refrence to 'https://graphics.stanford.edu/~seander/bithacks.html#ParityParallel'.
+ */
+
+static inline unsigned int __arch_parity4(unsigned int w)
+{
+	w &= 0xf;
+	return (0x6996 >> w) & 1;
+}
+
+static inline unsigned int __arch_parity8(unsigned int w)
+{
+	w ^= w >> 4;
+	return __arch_parity4(w);
+}
+
+static inline unsigned int __arch_parity16(unsigned int w)
+{
+	w ^= w >> 8;
+	return __arch_parity8(w);
+}
+
+static inline unsigned int __arch_parity32(unsigned int w)
+{
+	w ^= w >> 16;
+	return __arch_parity16(w);
+}
+
+static inline unsigned int __arch_parity64(__u64 w)
+{
+	return __arch_parity32((unsigned int)(w >> 32) ^ (unsigned int)w);
+}
+
+#endif /* _ASM_GENERIC_BITOPS_ARCH_PARITY_H_ */
diff --git a/include/asm-generic/bitops/const_parity.h b/include/asm-generic/bitops/const_parity.h
new file mode 100644
index 0000000..9590315
--- /dev/null
+++ b/include/asm-generic/bitops/const_parity.h
@@ -0,0 +1,36 @@
+#ifndef _ASM_GENERIC_BITOPS_CONST_PARITY_H_
+#define _ASM_GENERIC_BITOPS_CONST_PARITY_H_
+
+/*
+ * Compile time versions of __arch_parityN()
+ */
+#define __const_parity4(w)   ((0x6996 >> ((w) & 0xf)) & 1)
+#define __const_parity8(w)   (__const_parity4(w ^ (w >> 4)))
+#define __const_parity16(w)  (__const_parity8(w ^ (w >> 8)))
+#define __const_parity32(w)  (__const_parity16(w ^ (w >> 16)))
+#define __const_parity64(w)  (__const_parity32(w ^ (w >> 32)))
+
+/*
+ * Generic interface.
+ */
+#define parity4(w)   (__builtin_constant_p(w) ? __const_parity4(w)  : __arch_parity4(w))
+#define parity8(w)   (__builtin_constant_p(w) ? __const_parity8(w)  : __arch_parity8(w))
+#define parity16(w)  (__builtin_constant_p(w) ? __const_parity16(w) : __arch_parity16(w))
+#define parity32(w)  (__builtin_constant_p(w) ? __const_parity32(w) : __arch_parity32(w))
+#define parity64(w)  (__builtin_constant_p(w) ? __const_parity64(w) : __arch_parity64(w))
+
+/*
+ * Interface for known constant arguments
+ */
+#define PARITY4(w)   (BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) + __const_parity4(w))
+#define PARITY8(w)   (BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) + __const_parity8(w))
+#define PARITY16(w)  (BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) + __const_parity16(w))
+#define PARITY32(w)  (BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) + __const_parity32(w))
+#define PARITY64(w)  (BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) + __const_parity64(w))
+
+/*
+ * Type invariant interface to the compile time constant parity functions.
+ */
+#define PARITY(w)    PARITY64((u64)w)
+
+#endif /* _ASM_GENERIC_BITOPS_CONST_PARITY_H_ */
diff --git a/include/asm-generic/bitops/parity.h b/include/asm-generic/bitops/parity.h
new file mode 100644
index 0000000..a91dce7
--- /dev/null
+++ b/include/asm-generic/bitops/parity.h
@@ -0,0 +1,7 @@
+#ifndef _ASM_GENERIC_BITOPS_PARITY_H_
+#define _ASM_GENERIC_BITOPS_PARITY_H_
+
+#include <asm-generic/bitops/arch_parity.h>
+#include <asm-generic/bitops/const_parity.h>
+
+#endif /* _ASM_GENERIC_BITOPS_PARITY_H_ */
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index defeaac..f91cb44 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -80,6 +80,11 @@ static __always_inline unsigned long hweight_long(unsigned long w)
 	return sizeof(w) == 4 ? hweight32(w) : hweight64(w);
 }
 
+static __always_inline unsigned int parity_long(unsigned long w)
+{
+	return sizeof(w) == 4 ? parity32(w) : parity64(w);
+}
+
 /**
  * rol64 - rotate a 64-bit value left
  * @word: value to rotate
-- 
2.5.0