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authorBob Pearson <rpearson@systemfabricworks.com>2012-03-23 15:02:23 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-23 16:58:37 -0700
commit9a1dbf6a29694c9d81b498019f103aee0f8b5b6c (patch)
tree1f331fa108ea29ccf06a7b5816da4dbcaa12bf2d /lib/crc32defs.h
parentce4320ddda4c2520fe77194d3c801ad4e8a8aa11 (diff)
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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>
Diffstat (limited to 'lib/crc32defs.h')
-rw-r--r--lib/crc32defs.h18
1 files changed, 10 insertions, 8 deletions
diff --git a/lib/crc32defs.h b/lib/crc32defs.h
index f5a54017657..daa3a5e85f6 100644
--- a/lib/crc32defs.h
+++ b/lib/crc32defs.h
@@ -6,27 +6,29 @@
#define CRCPOLY_LE 0xedb88320
#define CRCPOLY_BE 0x04c11db7
-/* How many bits at a time to use. Requires a table of 4<<CRC_xx_BITS bytes. */
-/* For less performance-sensitive, use 4 */
+/* How many bits at a time to use. Valid values are 1, 2, 4, 8, and 32. */
+/* For less performance-sensitive, use 4 or 8 */
#ifndef CRC_LE_BITS
-# define CRC_LE_BITS 8
+# define CRC_LE_BITS 32
#endif
#ifndef CRC_BE_BITS
-# define CRC_BE_BITS 8
+# define CRC_BE_BITS 32
#endif
/*
* Little-endian CRC computation. Used with serial bit streams sent
* lsbit-first. Be sure to use cpu_to_le32() to append the computed CRC.
*/
-#if CRC_LE_BITS > 8 || CRC_LE_BITS < 1 || CRC_LE_BITS & CRC_LE_BITS-1
-# error CRC_LE_BITS must be a power of 2 between 1 and 8
+#if CRC_LE_BITS > 32 || CRC_LE_BITS < 1 || CRC_LE_BITS == 16 || \
+ CRC_LE_BITS & CRC_LE_BITS-1
+# error "CRC_LE_BITS must be one of {1, 2, 4, 8, 32}"
#endif
/*
* Big-endian CRC computation. Used with serial bit streams sent
* msbit-first. Be sure to use cpu_to_be32() to append the computed CRC.
*/
-#if CRC_BE_BITS > 8 || CRC_BE_BITS < 1 || CRC_BE_BITS & CRC_BE_BITS-1
-# error CRC_BE_BITS must be a power of 2 between 1 and 8
+#if CRC_BE_BITS > 32 || CRC_BE_BITS < 1 || CRC_BE_BITS == 16 || \
+ CRC_BE_BITS & CRC_BE_BITS-1
+# error "CRC_BE_BITS must be one of {1, 2, 4, 8, 32}"
#endif