From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Thu, 21 May 2015 07:10:59 +0000 (+0800)
Subject: crypto: scatterwalk - Add scatterwalk_ffwd helper
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=fc42bcba97bae738f905b83741134a63af7e6c02;p=linux-beck.git

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 3bd749c7bb70..db920b59a6c3 100644
--- a/crypto/scatterwalk.c
+++ b/crypto/scatterwalk.c
@@ -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);
diff --git a/include/crypto/scatterwalk.h b/include/crypto/scatterwalk.h
index 20e4226a2e14..96670e7e7c14 100644
--- a/include/crypto/scatterwalk.h
+++ b/include/crypto/scatterwalk.h
@@ -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 */