81 lines
2.2 KiB
Diff
81 lines
2.2 KiB
Diff
From c450dd0d27ff5cd7b83084e381e0cc808db2554e Mon Sep 17 00:00:00 2001
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From: Darren Salt <linux@youmustbejoking.demon.co.uk>
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Date: Sat, 11 Apr 2009 15:40:04 +0100
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Subject: [PATCH] crc-itu-t: add bit-reversed calculation
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Signed-off-by: Darren Salt <linux@youmustbejoking.demon.co.uk>
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---
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include/linux/crc-itu-t.h | 10 ++++++++++
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lib/crc-itu-t.c | 18 ++++++++++++++++++
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2 files changed, 28 insertions(+), 0 deletions(-)
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diff --git a/include/linux/crc-itu-t.h b/include/linux/crc-itu-t.h
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index 84920f3..7b2b7ba 100644
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--- a/include/linux/crc-itu-t.h
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+++ b/include/linux/crc-itu-t.h
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@@ -6,6 +6,9 @@
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* Poly 0x0x1021 (x^16 + x^12 + x^15 + 1)
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* Init 0
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*
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+ * The bit-reversed buffer variants may be non-standard, but some firmware
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+ * loaders require them.
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+ *
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* This source code is licensed under the GNU General Public License,
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* Version 2. See the file COPYING for more details.
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*/
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@@ -14,15 +17,22 @@
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#define CRC_ITU_T_H
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#include <linux/types.h>
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+#include <linux/bitrev.h>
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extern u16 const crc_itu_t_table[256];
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extern u16 crc_itu_t(u16 crc, const u8 *buffer, size_t len);
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+extern u16 crc_itu_t_bitreversed(u16 crc, const u8 *buffer, size_t len);
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static inline u16 crc_itu_t_byte(u16 crc, const u8 data)
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{
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return (crc << 8) ^ crc_itu_t_table[((crc >> 8) ^ data) & 0xff];
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}
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+static inline u16 crc_itu_t_bitreversed_byte(u16 crc, const u8 data)
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+{
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+ return (crc << 8) ^ crc_itu_t_table[((crc >> 8) ^ bitrev8(data)) & 0xff];
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+}
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+
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#endif /* CRC_ITU_T_H */
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diff --git a/lib/crc-itu-t.c b/lib/crc-itu-t.c
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index a63472b..886981e 100644
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--- a/lib/crc-itu-t.c
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+++ b/lib/crc-itu-t.c
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@@ -64,6 +64,24 @@ u16 crc_itu_t(u16 crc, const u8 *buffer, size_t len)
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}
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EXPORT_SYMBOL(crc_itu_t);
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+/**
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+ * crc_itu_t_byte_reversed - Compute the CRC-ITU-T for the data buffer;
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+ * the buffer content is assumed to be bit-reversed
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+ *
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+ * @crc: previous CRC value
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+ * @buffer: data pointer
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+ * @len: number of bytes in the buffer
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+ *
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+ * Returns the updated CRC value
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+ */
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+u16 crc_itu_t_bitreversed(u16 crc, const u8 *buffer, size_t len)
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+{
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+ while (len--)
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+ crc = crc_itu_t_bitreversed_byte(crc, *buffer++);
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+ return crc;
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+}
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+EXPORT_SYMBOL(crc_itu_t_bitreversed);
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+
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MODULE_DESCRIPTION("CRC ITU-T V.41 calculations");
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MODULE_LICENSE("GPL");
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--
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1.5.6.5
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