Return-path: Received: from mail-ew0-f176.google.com ([209.85.219.176]:41670 "EHLO mail-ew0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753041AbZFAOzN (ORCPT ); Mon, 1 Jun 2009 10:55:13 -0400 From: Dmitry Eremin-Solenikov To: linux-kernel@vger.kernel.org Cc: netdev@vger.kernel.org, linux-wireless@vger.kernel.org, slapin@ossfans.org, maxim.osipov@siemens.com, dmitry.baryshkov@siemens.com, oliver.fendt@siemens.com, Darren Salt Subject: [PATCH 01/10] crc-itu-t: add bit-reversed calculation Date: Mon, 1 Jun 2009 18:54:42 +0400 Message-Id: <1243868091-5315-2-git-send-email-dbaryshkov@gmail.com> In-Reply-To: <1243868091-5315-1-git-send-email-dbaryshkov@gmail.com> References: <1243868091-5315-1-git-send-email-dbaryshkov@gmail.com> Sender: linux-wireless-owner@vger.kernel.org List-ID: From: Darren Salt Signed-off-by: Darren Salt --- include/linux/crc-itu-t.h | 10 ++++++++++ lib/crc-itu-t.c | 18 ++++++++++++++++++ 2 files changed, 28 insertions(+), 0 deletions(-) diff --git a/include/linux/crc-itu-t.h b/include/linux/crc-itu-t.h index 84920f3..7b2b7ba 100644 --- a/include/linux/crc-itu-t.h +++ b/include/linux/crc-itu-t.h @@ -6,6 +6,9 @@ * Poly 0x0x1021 (x^16 + x^12 + x^15 + 1) * Init 0 * + * The bit-reversed buffer variants may be non-standard, but some firmware + * loaders require them. + * * This source code is licensed under the GNU General Public License, * Version 2. See the file COPYING for more details. */ @@ -14,15 +17,22 @@ #define CRC_ITU_T_H #include +#include extern u16 const crc_itu_t_table[256]; extern u16 crc_itu_t(u16 crc, const u8 *buffer, size_t len); +extern u16 crc_itu_t_bitreversed(u16 crc, const u8 *buffer, size_t len); static inline u16 crc_itu_t_byte(u16 crc, const u8 data) { return (crc << 8) ^ crc_itu_t_table[((crc >> 8) ^ data) & 0xff]; } +static inline u16 crc_itu_t_bitreversed_byte(u16 crc, const u8 data) +{ + return (crc << 8) ^ crc_itu_t_table[((crc >> 8) ^ bitrev8(data)) & 0xff]; +} + #endif /* CRC_ITU_T_H */ diff --git a/lib/crc-itu-t.c b/lib/crc-itu-t.c index a63472b..5562fdd 100644 --- a/lib/crc-itu-t.c +++ b/lib/crc-itu-t.c @@ -64,6 +64,24 @@ u16 crc_itu_t(u16 crc, const u8 *buffer, size_t len) } EXPORT_SYMBOL(crc_itu_t); +/** + * crc_itu_t_bitreversed - Compute the CRC-ITU-T for the data buffer; + * the buffer content is assumed to be bit-reversed + * + * @crc: previous CRC value + * @buffer: data pointer + * @len: number of bytes in the buffer + * + * Returns the updated CRC value + */ +u16 crc_itu_t_bitreversed(u16 crc, const u8 *buffer, size_t len) +{ + while (len--) + crc = crc_itu_t_bitreversed_byte(crc, *buffer++); + return crc; +} +EXPORT_SYMBOL(crc_itu_t_bitreversed); + MODULE_DESCRIPTION("CRC ITU-T V.41 calculations"); MODULE_LICENSE("GPL"); -- 1.6.2.4