From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752717Ab3LJTLP (ORCPT ); Tue, 10 Dec 2013 14:11:15 -0500 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:55534 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751374Ab3LJTLN (ORCPT ); Tue, 10 Dec 2013 14:11:13 -0500 From: Will Deacon To: linux-kernel@vger.kernel.org Cc: viro@zeniv.linux.org.uk, torvalds@linux-foundation.org, Will Deacon Subject: [PATCH 2/2] word-at-a-time: provide generic big-endian zero_bytemask implementation Date: Tue, 10 Dec 2013 19:10:58 +0000 Message-Id: <1386702658-21430-2-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 1.8.2.2 In-Reply-To: <1386702658-21430-1-git-send-email-will.deacon@arm.com> References: <1386702658-21430-1-git-send-email-will.deacon@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Whilst architectures may be able to do better than this (which they can, by simply defining their own macro), this is a generic stab at a zero_bytemask implementation for the asm-generic, big-endian word-at-a-time implementation. On arm64, a clz instruction is used to implement the fls efficiently. Signed-off-by: Will Deacon --- I'm happy to move this into the arch/ backends, but there's a strong linkage between this and the generic word-at-a-time algorithm that could easily break if they don't live together. include/asm-generic/word-at-a-time.h | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/include/asm-generic/word-at-a-time.h b/include/asm-generic/word-at-a-time.h index 3f21f1b72e45..d3909effd725 100644 --- a/include/asm-generic/word-at-a-time.h +++ b/include/asm-generic/word-at-a-time.h @@ -49,4 +49,12 @@ static inline bool has_zero(unsigned long val, unsigned long *data, const struct return (val + c->high_bits) & ~rhs; } +#ifndef zero_bytemask +#ifdef CONFIG_64BIT +#define zero_bytemask(mask) (~0ul << fls64(mask)) +#else +#define zero_bytemask(mask) (~0ul << fls(mask)) +#endif /* CONFIG_64BIT */ +#endif /* zero_bytemask */ + #endif /* _ASM_WORD_AT_A_TIME_H */ -- 1.8.2.2