Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754615AbYCORdH (ORCPT ); Sat, 15 Mar 2008 13:33:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752112AbYCORck (ORCPT ); Sat, 15 Mar 2008 13:32:40 -0400 Received: from theia.rz.uni-saarland.de ([134.96.7.31]:13090 "EHLO theia.rz.uni-saarland.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752030AbYCORcj (ORCPT ); Sat, 15 Mar 2008 13:32:39 -0400 Date: Sat, 15 Mar 2008 18:30:57 +0100 From: Alexander van Heukelum To: Andrew Morton , linux-arch Cc: Ingo Molnar , Andi Kleen , LKML , heukelum@fastmail.fm Subject: [1/3] Introduce a generic __fls implementation Message-ID: <20080315173056.GA21659@mailshack.com> References: <20080315172913.GA21648@mailshack.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080315172913.GA21648@mailshack.com> User-Agent: Mutt/1.5.9i X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-3.0 (theia.rz.uni-saarland.de [134.96.7.31]); Sat, 15 Mar 2008 18:31:48 +0100 (CET) X-AntiVirus: checked by AntiVir MailGate (version: 2.1.2-14; AVE: 7.6.0.73; VDF: 7.0.3.31; host: AntiVir1) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1765 Lines: 65 Add a generic __fls implementation in the same spirit as the generic __ffs one. It finds the last (most significant) set bit in the given long value. Signed-off-by: Alexander van Heukelum --- include/asm-generic/bitops/__fls.h | 43 ++++++++++++++++++++++++++++++++++++ 1 files changed, 43 insertions(+), 0 deletions(-) create mode 100644 include/asm-generic/bitops/__fls.h diff --git a/include/asm-generic/bitops/__fls.h b/include/asm-generic/bitops/__fls.h new file mode 100644 index 0000000..be24465 --- /dev/null +++ b/include/asm-generic/bitops/__fls.h @@ -0,0 +1,43 @@ +#ifndef _ASM_GENERIC_BITOPS___FLS_H_ +#define _ASM_GENERIC_BITOPS___FLS_H_ + +#include + +/** + * __fls - find last (most-significant) set bit in a long word + * @word: the word to search + * + * Undefined if no set bit exists, so code should check against 0 first. + */ +static inline unsigned long __fls(unsigned long word) +{ + int num = BITS_PER_LONG - 1; + +#if BITS_PER_LONG == 64 + if (!(word & (~0ul << 32))) { + num -= 32; + word <<= 32; + } +#endif + if (!(word & (~0ul << (BITS_PER_LONG-16)))) { + num -= 16; + word <<= 16; + } + if (!(word & (~0ul << (BITS_PER_LONG-8)))) { + num -= 8; + word <<= 8; + } + if (!(word & (~0ul << (BITS_PER_LONG-4)))) { + num -= 4; + word <<= 4; + } + if (!(word & (~0ul << (BITS_PER_LONG-2)))) { + num -= 2; + word <<= 2; + } + if (!(word & (~0ul << (BITS_PER_LONG-1)))) + num -= 1; + return num; +} + +#endif /* _ASM_GENERIC_BITOPS___FLS_H_ */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/