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-rw-r--r--include/linux/scatterlist.h38
1 files changed, 38 insertions, 0 deletions
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 71fc8136004..e5996984ddd 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -224,4 +224,42 @@ size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
*/
#define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))
+
+/*
+ * Mapping sg iterator
+ *
+ * Iterates over sg entries mapping page-by-page. On each successful
+ * iteration, @miter->page points to the mapped page and
+ * @miter->length bytes of data can be accessed at @miter->addr. As
+ * long as an interation is enclosed between start and stop, the user
+ * is free to choose control structure and when to stop.
+ *
+ * @miter->consumed is set to @miter->length on each iteration. It
+ * can be adjusted if the user can't consume all the bytes in one go.
+ * Also, a stopped iteration can be resumed by calling next on it.
+ * This is useful when iteration needs to release all resources and
+ * continue later (e.g. at the next interrupt).
+ */
+
+#define SG_MITER_ATOMIC (1 << 0) /* use kmap_atomic */
+
+struct sg_mapping_iter {
+ /* the following three fields can be accessed directly */
+ struct page *page; /* currently mapped page */
+ void *addr; /* pointer to the mapped area */
+ size_t length; /* length of the mapped area */
+ size_t consumed; /* number of consumed bytes */
+
+ /* these are internal states, keep away */
+ struct scatterlist *__sg; /* current entry */
+ unsigned int __nents; /* nr of remaining entries */
+ unsigned int __offset; /* offset within sg */
+ unsigned int __flags;
+};
+
+void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
+ unsigned int nents, unsigned int flags);
+bool sg_miter_next(struct sg_mapping_iter *miter);
+void sg_miter_stop(struct sg_mapping_iter *miter);
+
#endif /* _LINUX_SCATTERLIST_H */