From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752232AbaLOQTR (ORCPT ); Mon, 15 Dec 2014 11:19:17 -0500 Received: from mx02.posteo.de ([89.146.194.165]:32853 "EHLO mx02.posteo.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752090AbaLOQTM (ORCPT ); Mon, 15 Dec 2014 11:19:12 -0500 From: Martin Kepplinger To: peterz@infradead.org Cc: mingo@kernel.org, tytso@mit.edu, linux-kernel@vger.kernel.org, Martin Kepplinger Subject: [PATCH 1/6] bitops.h: add sign_extend8 function Date: Mon, 15 Dec 2014 17:18:32 +0100 Message-Id: <1418660317-21750-2-git-send-email-martink@posteo.de> X-Mailer: git-send-email 2.1.3 In-Reply-To: <1418660317-21750-1-git-send-email-martink@posteo.de> References: <1418660317-21750-1-git-send-email-martink@posteo.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This adds a helper function that extends any signed value smaller than 8 bits to a s8. Signed-off-by: Martin Kepplinger --- include/linux/bitops.h | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 5d858e0..3c2a539 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -161,6 +161,17 @@ static inline __u8 ror8(__u8 word, unsigned int shift) } /** + * sign_extend8 - sign extend a 8-bit value using specified bit as sign-bit + * @value: value to sign extend + * @index: 0 based bit index (0<=index<8) to sign bit + */ +static inline __s8 sign_extend8(__u8 value, int index) +{ + __u8 shift = 7 - index; + return (__s8)(value << shift) >> shift; +} + +/** * sign_extend32 - sign extend a 32-bit value using specified bit as sign-bit * @value: value to sign extend * @index: 0 based bit index (0<=index<32) to sign bit -- 2.1.3