@@ -380,6 +380,10 @@ static inline unsigned long ffz(unsigned long word)
* @word: The word to search
*
* Undefined if no set bit exists, so code should check against 0 first.
+ *
+ * Note: __fls(x) is equivalent to fls(x) - 1. That is, __fls() uses
+ * a zero-based indexing scheme (0 to BITS_PER_LONG - 1), where
+ * __fls(1) = 0, __fls(2) = 1, and so on.
*/
static inline unsigned long __fls(unsigned long word)
{
@@ -8,6 +8,11 @@
* @word: the word to search
*
* Undefined if no set bit exists, so code should check against 0 first.
+ *
+ * Note: __fls(x) is equivalent to fls(x) - 1. That is, __fls() uses
+ * a zero-based indexing scheme (0 to BITS_PER_LONG - 1), where
+ * __fls(1) = 0, __fls(2) = 1, and so on.
+ *
*/
static __always_inline unsigned long __fls(unsigned long word)
{
fls() indexes the bits starting with 1, ie., from 1 to BITS_PER_LONG whereas __fls() uses a zero-based indexing scheme (0 to BITS_PER_LONG - 1). Add comments to document this important difference. Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> --- arch/x86/include/asm/bitops.h | 4 ++++ include/asm-generic/bitops/__fls.h | 5 +++++ 2 files changed, 9 insertions(+) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html