crypto: scatterwalk - Change scatterwalk_next calling convention

Rather than returning the address and storing the length into an
argument pointer, add an address field to the walk struct and use
that to store the address.  The length is returned directly.

Change the done functions to use this stored address instead of
getting them from the caller.

Split the address into two using a union.  The user should only
access the const version so that it is never changed.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

2 files changed, 25 insertions, 17 deletions

diff --git a/include/crypto/algapi.h b/include/crypto/algapi.h
index 94989b2e1350..f92e22686a68 100644
--- a/include/crypto/algapi.h
+++ b/include/crypto/algapi.h
@@ -54,6 +54,7 @@ struct rtattr;
 struct scatterlist;
 struct seq_file;
 struct sk_buff;
+union crypto_no_such_thing;
 
 struct crypto_instance {
 	struct crypto_alg alg;
@@ -108,6 +109,12 @@ struct crypto_queue {
 struct scatter_walk {
 	struct scatterlist *sg;
 	unsigned int offset;
+	union {
+		void *const addr;
+
+		/* Private API field, do not touch. */
+		union crypto_no_such_thing *__addr;
+	};
 };
 
 struct crypto_attr_alg {
diff --git a/include/crypto/scatterwalk.h b/include/crypto/scatterwalk.h
index 3024adbdd443..8523c7591d95 100644
--- a/include/crypto/scatterwalk.h
+++ b/include/crypto/scatterwalk.h
@@ -120,18 +120,20 @@ static inline void *scatterwalk_map(struct scatter_walk *walk)
  * scatterwalk_next() - Get the next data buffer in a scatterlist walk
  * @walk: the scatter_walk
  * @total: the total number of bytes remaining, > 0
- * @nbytes_ret: (out) the next number of bytes available, <= @total
  *
- * Return: A virtual address for the next segment of data from the scatterlist.
- *	   The caller must call scatterwalk_done_src() or scatterwalk_done_dst()
- *	   when it is done using this virtual address.
+ * A virtual address for the next segment of data from the scatterlist will
+ * be placed into @walk->addr.  The caller must call scatterwalk_done_src()
+ * or scatterwalk_done_dst() when it is done using this virtual address.
+ *
+ * Returns: the next number of bytes available, <= @total
  */
-static inline void *scatterwalk_next(struct scatter_walk *walk,
-				     unsigned int total,
-				     unsigned int *nbytes_ret)
+static inline unsigned int scatterwalk_next(struct scatter_walk *walk,
+					    unsigned int total)
 {
-	*nbytes_ret = scatterwalk_clamp(walk, total);
-	return scatterwalk_map(walk);
+	unsigned int nbytes = scatterwalk_clamp(walk, total);
+
+	walk->__addr = scatterwalk_map(walk);
+	return nbytes;
 }
 
 static inline void scatterwalk_unmap(const void *vaddr)
@@ -149,32 +151,31 @@ static inline void scatterwalk_advance(struct scatter_walk *walk,
 /**
  * scatterwalk_done_src() - Finish one step of a walk of source scatterlist
  * @walk: the scatter_walk
- * @vaddr: the address returned by scatterwalk_next()
  * @nbytes: the number of bytes processed this step, less than or equal to the
  *	    number of bytes that scatterwalk_next() returned.
  *
- * Use this if the @vaddr was not written to, i.e. it is source data.
+ * Use this if the mapped address was not written to, i.e. it is source data.
  */
 static inline void scatterwalk_done_src(struct scatter_walk *walk,
-					const void *vaddr, unsigned int nbytes)
+					unsigned int nbytes)
 {
-	scatterwalk_unmap(vaddr);
+	scatterwalk_unmap(walk->addr);
 	scatterwalk_advance(walk, nbytes);
 }
 
 /**
  * scatterwalk_done_dst() - Finish one step of a walk of destination scatterlist
  * @walk: the scatter_walk
- * @vaddr: the address returned by scatterwalk_next()
  * @nbytes: the number of bytes processed this step, less than or equal to the
  *	    number of bytes that scatterwalk_next() returned.
  *
- * Use this if the @vaddr may have been written to, i.e. it is destination data.
+ * Use this if the mapped address may have been written to, i.e. it is
+ * destination data.
  */
 static inline void scatterwalk_done_dst(struct scatter_walk *walk,
-					void *vaddr, unsigned int nbytes)
+					unsigned int nbytes)
 {
-	scatterwalk_unmap(vaddr);
+	scatterwalk_unmap(walk->addr);
 	/*
 	 * Explicitly check ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE instead of just
 	 * relying on flush_dcache_page() being a no-op when not implemented,