x86: generic versions of find_first_(zero_)bit, convert i386

Generic versions of __find_first_bit and __find_first_zero_bit
are introduced as simplified versions of __find_next_bit and
__find_next_zero_bit. Their compilation and use are guarded by
a new config variable GENERIC_FIND_FIRST_BIT.

The generic versions of find_first_bit and find_first_zero_bit
are implemented in terms of the newly introduced __find_first_bit
and __find_first_zero_bit.

This patch does not remove the i386-specific implementation,
but it does switch i386 to use the generic functions by setting
GENERIC_FIND_FIRST_BIT=y for X86_32.

Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 36 insertions, 0 deletions

diff --git a/include/asm-x86/bitops_32.h b/include/asm-x86/bitops_32.h
index 3ed64b2..ba2c0de 100644
--- a/include/asm-x86/bitops_32.h
+++ b/include/asm-x86/bitops_32.h
@@ -5,6 +5,7 @@
  * Copyright 1992, Linus Torvalds.
  */
 
+#ifndef CONFIG_GENERIC_FIND_FIRST_BIT
 /**
  * find_first_zero_bit - find the first zero bit in a memory region
  * @addr: The address to start the search at
@@ -59,6 +60,7 @@ static inline unsigned find_first_bit(const unsigned long *addr, unsigned size)
 	}
 	return x;
 }
+#endif
 
 #ifdef __KERNEL__
 
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 3865f2c..355d67b 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -113,6 +113,40 @@ static inline unsigned fls_long(unsigned long l)
 }
 
 #ifdef __KERNEL__
+#ifdef CONFIG_GENERIC_FIND_FIRST_BIT
+extern unsigned long __find_first_bit(const unsigned long *addr,
+		unsigned long size);
+
+/**
+ * find_first_bit - find the first set bit in a memory region
+ * @addr: The address to start the search at
+ * @size: The maximum size to search
+ *
+ * Returns the bit number of the first set bit.
+ */
+static __always_inline unsigned long
+find_first_bit(const unsigned long *addr, unsigned long size)
+{
+	return __find_first_bit(addr, size);
+}
+
+extern unsigned long __find_first_zero_bit(const unsigned long *addr,
+		unsigned long size);
+
+/**
+ * find_first_zero_bit - find the first cleared bit in a memory region
+ * @addr: The address to start the search at
+ * @size: The maximum size to search
+ *
+ * Returns the bit number of the first cleared bit.
+ */
+static __always_inline unsigned long
+find_first_zero_bit(const unsigned long *addr, unsigned long size)
+{
+	return __find_first_zero_bit(addr, size);
+}
+#endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
+
 #ifdef CONFIG_GENERIC_FIND_NEXT_BIT
 extern unsigned long __find_next_bit(const unsigned long *addr,
 		unsigned long size, unsigned long offset);