[PATCH RFC 1/6] Add support for userspace ceph DECODE_START.

[Douglas Fuller <dfuller@redhat.com>]

From: Mike Christie <michaelc@cs.wisc.edu>

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
---
 include/linux/ceph/decode.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/include/linux/ceph/decode.h b/include/linux/ceph/decode.h
index a6ef9cc..b55c7fd 100644
--- a/include/linux/ceph/decode.h
+++ b/include/linux/ceph/decode.h
@@ -255,5 +255,28 @@ static inline void ceph_encode_string(void **p, void *end,
 		ceph_encode_string(p, end, s, n);		\
 	} while (0)
 
+/**
+ * ceph_start_decoding - start a decoding block
+ * @p: buffer to decode
+ * @end: end of buffer
+ * @curr_ver: current version of the encoding that the code supports/encode
+ * @len: buffer to return len of data in buffer
+ */
+static inline int ceph_start_decoding(void **p, void *end, u8 curr_ver,
+				      u32 *len)
+{
+	u8 struct_ver, struct_compat;
+
+	ceph_decode_8_safe(p, end, struct_ver, fail);
+	ceph_decode_8_safe(p, end, struct_compat, fail);
+
+	if (curr_ver < struct_compat)
+		return -EINVAL;
+
+	ceph_decode_32_safe(p, end, *len, fail);
+	return 0;
+fail:
+	return -ERANGE;
+}
 
 #endif
-- 
1.9.3