greybus: only record message payload size

An asynchronous operation will want to know how big the response
message it receives is.  Rather than require the sender to record
that information, expose a new field "payload_size" available to
the protocol code for this purpose.

An operation message consists of a header and a payload.  The size
of the message can be derived from the size of the payload, so
record only the payload size and not the size of the whole message.
Reorder the fields in a message structure.

Update the description of the message header structure.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

1 files changed, 9 insertions, 4 deletions

diff --git a/drivers/staging/greybus/operation.h b/drivers/staging/greybus/operation.h
index 3415e8b56eb6..a79e88a3b314 100644
--- a/drivers/staging/greybus/operation.h
+++ b/drivers/staging/greybus/operation.h
@@ -38,13 +38,18 @@ enum gb_operation_result {
 	GB_OP_MALFUNCTION	= 0xff,
 };
 
+/*
+ * Protocol code should only examine the payload and payload_size
+ * fields.  All other fields are intended to be private to the
+ * operations core code.
+ */
 struct gb_message {
-	struct gb_operation_msg_hdr	*header;
-	void				*payload;
-	size_t				size;	/* header + payload */
 	struct gb_operation		*operation;
-
 	void				*cookie;
+	struct gb_operation_msg_hdr	*header;
+
+	void				*payload;
+	size_t				payload_size;
 
 	u8				buffer[];
 };