crypto: scatterwalk - Add scatterwalk_ffwd helper
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>
diff --git a/crypto/scatterwalk.c b/crypto/scatterwalk.c
index 3bd749c..db920b5 100644
--- a/crypto/scatterwalk.c
+++ b/crypto/scatterwalk.c
@@ -146,3 +146,25 @@
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);