From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx130.postini.com [74.125.245.130]) by kanga.kvack.org (Postfix) with SMTP id CFD2A6B0071 for ; Fri, 30 Aug 2013 09:21:32 -0400 (EDT) Received: from /spool/local by e8.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 30 Aug 2013 14:21:31 +0100 Received: from b01cxnp22034.gho.pok.ibm.com (b01cxnp22034.gho.pok.ibm.com [9.57.198.24]) by d01dlp01.pok.ibm.com (Postfix) with ESMTP id 99E5938C8045 for ; Fri, 30 Aug 2013 09:21:29 -0400 (EDT) Received: from d01av02.pok.ibm.com (d01av02.pok.ibm.com [9.56.224.216]) by b01cxnp22034.gho.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r7UDLTJe29229198 for ; Fri, 30 Aug 2013 13:21:29 GMT Received: from d01av02.pok.ibm.com (loopback [127.0.0.1]) by d01av02.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r7UDLQ7m029952 for ; Fri, 30 Aug 2013 10:21:29 -0300 From: "Srivatsa S. Bhat" Subject: [RFC PATCH v3 12/35] bitops: Document the difference in indexing between fls() and __fls() Date: Fri, 30 Aug 2013 18:47:31 +0530 Message-ID: <20130830131727.4947.86874.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20130830131221.4947.99764.stgit@srivatsabhat.in.ibm.com> References: <20130830131221.4947.99764.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org, mgorman@suse.de, hannes@cmpxchg.org, tony.luck@intel.com, matthew.garrett@nebula.com, dave@sr71.net, riel@redhat.com, arjan@linux.intel.com, srinivas.pandruvada@linux.intel.com, willy@linux.intel.com, kamezawa.hiroyu@jp.fujitsu.com, lenb@kernel.org, rjw@sisk.pl Cc: gargankita@gmail.com, paulmck@linux.vnet.ibm.com, svaidy@linux.vnet.ibm.com, andi@firstfloor.org, isimatu.yasuaki@jp.fujitsu.com, santosh.shilimkar@ti.com, kosaki.motohiro@gmail.com, srivatsa.bhat@linux.vnet.ibm.com, linux-pm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org 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 --- arch/x86/include/asm/bitops.h | 4 ++++ include/asm-generic/bitops/__fls.h | 5 +++++ 2 files changed, 9 insertions(+) diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h index 6dfd019..25e6fdc 100644 --- a/arch/x86/include/asm/bitops.h +++ b/arch/x86/include/asm/bitops.h @@ -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) { diff --git a/include/asm-generic/bitops/__fls.h b/include/asm-generic/bitops/__fls.h index a60a7cc..ae908a5 100644 --- a/include/asm-generic/bitops/__fls.h +++ b/include/asm-generic/bitops/__fls.h @@ -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) { -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org