bitops: introduce CONFIG_GENERIC_FIND_BIT_LE

This introduces CONFIG_GENERIC_FIND_BIT_LE to tell whether to use generic
implementation of find_*_bit_le() in lib/find_next_bit.c or not.

For now we select CONFIG_GENERIC_FIND_BIT_LE for all architectures which
enable CONFIG_GENERIC_FIND_NEXT_BIT.

But m68knommu wants to define own faster find_next_zero_bit_le() and
continues using generic find_next_{,zero_}bit().
(CONFIG_GENERIC_FIND_NEXT_BIT and !CONFIG_GENERIC_FIND_BIT_LE)

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Greg Ungerer <gerg@uclinux.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/Kconfig

@@ -22,6 +22,9 @@ config GENERIC_FIND_FIRST_BIT
 config GENERIC_FIND_NEXT_BIT
 	bool
 
+config GENERIC_FIND_BIT_LE
+	bool
+
 config GENERIC_FIND_LAST_BIT
 	bool
 	default y

lib/Makefile

@@ -40,6 +40,7 @@ lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
 lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
 lib-$(CONFIG_GENERIC_FIND_FIRST_BIT) += find_next_bit.o
 lib-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o
+lib-$(CONFIG_GENERIC_FIND_BIT_LE) += find_next_bit.o
 obj-$(CONFIG_GENERIC_FIND_LAST_BIT) += find_last_bit.o
 
 CFLAGS_hweight.o = $(subst $(quote),,$(CONFIG_ARCH_HWEIGHT_CFLAGS))

lib/find_next_bit.c

@@ -160,6 +160,7 @@ EXPORT_SYMBOL(find_first_zero_bit);
 #endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
 
 #ifdef __BIG_ENDIAN
+#ifdef CONFIG_GENERIC_FIND_BIT_LE
 
 /* include/linux/byteorder does not support "unsigned long" type */
 static inline unsigned long ext2_swabp(const unsigned long * x)
@@ -273,4 +274,6 @@ found_middle_swap:
 	return result + __ffs(ext2_swab(tmp));
 }
 EXPORT_SYMBOL(find_next_bit_le);
+
+#endif /* CONFIG_GENERIC_FIND_BIT_LE */
 #endif /* __BIG_ENDIAN */