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crypto: scatterwalk - Add scatterwalk_ffwd helper

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This patch adds the scatterwalk_ffwd helper which can create an
SG list that starts in the middle of an existing SG list.  The
new list may either be part of the existing list or be a chain
that latches onto part of the existing list.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Herbert Xu 2015-05-21 15:10:59 +08:00
parent 66d948e732
commit fc42bcba97
2 changed files with 26 additions and 0 deletions
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22
crypto/scatterwalk.c
View file

@ -146,3 +146,25 @@ int scatterwalk_bytes_sglen(struct scatterlist *sg, int num_bytes)
return n;
}
EXPORT_SYMBOL_GPL(scatterwalk_bytes_sglen);
struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
struct scatterlist *src,
unsigned int len)
{
for (;;) {
if (!len)
return src;
if (src->length > len)
break;
len -= src->length;
src = sg_next(src);
}
sg_set_page(dst, sg_page(src), src->length - len, src->offset + len);
scatterwalk_crypto_chain(dst, sg_next(src), 0, 2);
return dst;
}
EXPORT_SYMBOL_GPL(scatterwalk_ffwd);

4
include/crypto/scatterwalk.h
View file

@ -102,4 +102,8 @@ void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
int scatterwalk_bytes_sglen(struct scatterlist *sg, int num_bytes);
struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
struct scatterlist *src,
unsigned int len);
#endif /* _CRYPTO_SCATTERWALK_H */