crypto: scatterwalk - Add support for calculating number of SG elements
Crypto layer only passes nbytes to encrypt but in omap-aes driver we need to
know number of SG elements to pass to dmaengine slave API. We add function for
the same to scatterwalk library.
Signed-off-by: Joel Fernandes <joelf@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/crypto/scatterwalk.c b/crypto/scatterwalk.c
index 7281b8a..79ca227 100644
--- a/crypto/scatterwalk.c
+++ b/crypto/scatterwalk.c
@@ -124,3 +124,25 @@
scatterwalk_done(&walk, out, 0);
}
EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);
+
+int scatterwalk_bytes_sglen(struct scatterlist *sg, int num_bytes)
+{
+ int offset = 0, n = 0;
+
+ /* num_bytes is too small */
+ if (num_bytes < sg->length)
+ return -1;
+
+ do {
+ offset += sg->length;
+ n++;
+ sg = scatterwalk_sg_next(sg);
+
+ /* num_bytes is too large */
+ if (unlikely(!sg && (num_bytes < offset)))
+ return -1;
+ } while (sg && (num_bytes > offset));
+
+ return n;
+}
+EXPORT_SYMBOL_GPL(scatterwalk_bytes_sglen);