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crc8: Support crc calculation across non-contiguous data

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Building a single buffer for crc calculation is often inefficient, so
add a new function that calculates crc8 from an existing crc8.

BUG=chromium:576911
BRANCH=None
TEST=Manual on sentry with subsequent commit. Verify that smbus
communication with battery is functional.

Change-Id: I05ffedb81ffcf0c126acda5f6212b3147b1580a1
Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/333786
Commit-Ready: Shawn N <shawnn@chromium.org>
Tested-by: Shawn N <shawnn@chromium.org>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
This commit is contained in:
Shawn Nematbakhsh
2016-03-15 16:00:09 -07:00
committed by chrome-bot
parent f06443e2f7
commit 952b2a54e1
2 changed files with 20 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
common/crc8.c
View File

@@ -5,9 +5,14 @@
#include "common.h"
#include "crc8.h"
uint8_t crc8(const uint8_t *data, int len)
inline uint8_t crc8(const uint8_t *data, int len)
{
unsigned crc = 0;
return crc8_arg(data, len, 0);
}
uint8_t crc8_arg(const uint8_t *data, int len, uint8_t previous_crc)
{
unsigned crc = previous_crc << 8;
int i, j;
for (j = len; j; j--, data++) {

14
include/crc8.h
View File

@@ -13,9 +13,21 @@
* algorithm would be faster, but for only a few bytes it isn't worth the code
* size.
* @param data uint8_t *, input, a pointer to input data
* @param len int, input, size of iput data in byte
* @param len int, input, size of input data in bytes
* @return the crc-8 of the input data.
*/
uint8_t crc8(const uint8_t *data, int len);
/**
* crc8_arg
* Return CRC-8 of the data, based upon pre-calculated partial CRC of previous
* data.
* @param data uint8_t *, input, a pointer to input data
* @param len int, input, size of input data in bytes
* @param previous_crc uint8_t, input, pre-calculated CRC of previous data.
* Seed with zero for a new calculation (or use the result of crc8()).
* @return the crc-8 of the input data.
*/
uint8_t crc8_arg(const uint8_t *data, int len, uint8_t previous_crc);
#endif /* __CROS_EC_CRC8_H */