crc32: make CRC_*_BITS definition correspond to actual bit counts
crc32.c provides a choice of one of several algorithms for computing the LSB and LSB versions of the CRC32 checksum based on the parameters CRC_LE_BITS and CRC_BE_BITS. In the original version the values 1, 2, 4 and 8 respectively selected versions of the alrogithm that computed the crc 1, 2, 4 and 32 bits as a time. This patch series adds a new version that computes the CRC 64 bits at a time. To make things easier to understand the parameter has been reinterpreted to actually stand for the number of bits processed in each step of the algorithm so that the old value 8 has been replaced with the value 32. This also allows us to add in a widely used crc algorithm that computes the crc 8 bits at a time called the Sarwate algorithm. [djwong@us.ibm.com: Minor changelog tweaks] Signed-off-by: Bob Pearson <rpearson@systemfabricworks.com> Signed-off-by: Darrick J. Wong <djwong@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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3 changed files with 34 additions and 12 deletions
17
lib/crc32.c
17
lib/crc32.c
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@ -27,13 +27,13 @@
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#include <linux/types.h>
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#include "crc32defs.h"
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#if CRC_LE_BITS == 8
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#if CRC_LE_BITS > 8
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# define tole(x) ((__force u32) __constant_cpu_to_le32(x))
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#else
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# define tole(x) (x)
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#endif
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#if CRC_BE_BITS == 8
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#if CRC_BE_BITS > 8
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# define tobe(x) ((__force u32) __constant_cpu_to_be32(x))
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#else
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# define tobe(x) (x)
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@ -45,7 +45,7 @@ MODULE_AUTHOR("Matt Domsch <Matt_Domsch@dell.com>");
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MODULE_DESCRIPTION("Ethernet CRC32 calculations");
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MODULE_LICENSE("GPL");
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#if CRC_LE_BITS == 8 || CRC_BE_BITS == 8
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#if CRC_LE_BITS > 8 || CRC_BE_BITS > 8
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static inline u32
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crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
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@ -126,6 +126,12 @@ u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
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crc = (crc >> 4) ^ crc32table_le[0][crc & 15];
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}
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# elif CRC_LE_BITS == 8
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/* aka Sarwate algorithm */
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while (len--) {
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crc ^= *p++;
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crc = (crc >> 8) ^ crc32table_le[0][crc & 255];
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}
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# else
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const u32 (*tab)[] = crc32table_le;
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crc = (__force u32) __cpu_to_le32(crc);
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@ -169,6 +175,11 @@ u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
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crc = (crc << 4) ^ crc32table_be[0][crc >> 28];
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}
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# elif CRC_BE_BITS == 8
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while (len--) {
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crc ^= *p++ << 24;
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crc = (crc << 8) ^ crc32table_be[0][crc >> 24];
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}
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# else
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const u32 (*tab)[] = crc32table_be;
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crc = (__force u32) __cpu_to_be32(crc);
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@ -6,27 +6,29 @@
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#define CRCPOLY_LE 0xedb88320
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#define CRCPOLY_BE 0x04c11db7
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/* How many bits at a time to use. Requires a table of 4<<CRC_xx_BITS bytes. */
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/* For less performance-sensitive, use 4 */
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/* How many bits at a time to use. Valid values are 1, 2, 4, 8, and 32. */
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/* For less performance-sensitive, use 4 or 8 */
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#ifndef CRC_LE_BITS
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# define CRC_LE_BITS 8
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# define CRC_LE_BITS 32
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#endif
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#ifndef CRC_BE_BITS
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# define CRC_BE_BITS 8
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# define CRC_BE_BITS 32
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#endif
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/*
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* Little-endian CRC computation. Used with serial bit streams sent
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* lsbit-first. Be sure to use cpu_to_le32() to append the computed CRC.
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*/
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#if CRC_LE_BITS > 8 || CRC_LE_BITS < 1 || CRC_LE_BITS & CRC_LE_BITS-1
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# error CRC_LE_BITS must be a power of 2 between 1 and 8
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#if CRC_LE_BITS > 32 || CRC_LE_BITS < 1 || CRC_LE_BITS == 16 || \
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CRC_LE_BITS & CRC_LE_BITS-1
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# error "CRC_LE_BITS must be one of {1, 2, 4, 8, 32}"
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#endif
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/*
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* Big-endian CRC computation. Used with serial bit streams sent
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* msbit-first. Be sure to use cpu_to_be32() to append the computed CRC.
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*/
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#if CRC_BE_BITS > 8 || CRC_BE_BITS < 1 || CRC_BE_BITS & CRC_BE_BITS-1
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# error CRC_BE_BITS must be a power of 2 between 1 and 8
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#if CRC_BE_BITS > 32 || CRC_BE_BITS < 1 || CRC_BE_BITS == 16 || \
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CRC_BE_BITS & CRC_BE_BITS-1
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# error "CRC_BE_BITS must be one of {1, 2, 4, 8, 32}"
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#endif
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@ -4,8 +4,17 @@
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#define ENTRIES_PER_LINE 4
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#if CRC_LE_BITS <= 8
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#define LE_TABLE_SIZE (1 << CRC_LE_BITS)
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#else
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#define LE_TABLE_SIZE 256
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#endif
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#if CRC_BE_BITS <= 8
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#define BE_TABLE_SIZE (1 << CRC_BE_BITS)
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#else
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#define BE_TABLE_SIZE 256
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#endif
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static uint32_t crc32table_le[4][256];
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static uint32_t crc32table_be[4][256];
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@ -24,7 +33,7 @@ static void crc32init_le(void)
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crc32table_le[0][0] = 0;
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for (i = 1 << (CRC_LE_BITS - 1); i; i >>= 1) {
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for (i = LE_TABLE_SIZE >> 1; i; i >>= 1) {
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crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
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for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
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crc32table_le[0][i + j] = crc ^ crc32table_le[0][j];
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