greybus: operation: move message-header definition to header file

Move operation message-header to operation.h so that it can be used
by host drivers.

Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/drivers/staging/greybus/operation.h b/drivers/staging/greybus/operation.h
index 6784f9832c8e..5ed1f6e3e97e 100644
--- a/drivers/staging/greybus/operation.h
+++ b/drivers/staging/greybus/operation.h
@@ -41,6 +41,35 @@ enum gb_operation_result {
 };
 
 /*
+ * All operation messages (both requests and responses) begin with
+ * a header that encodes the size of the message (header included).
+ * This header also contains a unique identifier, that associates a
+ * response message with its operation.  The header contains an
+ * operation type field, whose interpretation is dependent on what
+ * type of protocol is used over the connection.  The high bit
+ * (0x80) of the operation type field is used to indicate whether
+ * the message is a request (clear) or a response (set).
+ *
+ * Response messages include an additional result byte, which
+ * communicates the result of the corresponding request.  A zero
+ * result value means the operation completed successfully.  Any
+ * other value indicates an error; in this case, the payload of the
+ * response message (if any) is ignored.  The result byte must be
+ * zero in the header for a request message.
+ *
+ * The wire format for all numeric fields in the header is little
+ * endian.  Any operation-specific data begins immediately after the
+ * header, and is 64-bit aligned.
+ */
+struct gb_operation_msg_hdr {
+	__le16	size;		/* Size in bytes of header + payload */
+	__le16	operation_id;	/* Operation unique id */
+	__u8	type;		/* E.g GB_I2C_TYPE_* or GB_GPIO_TYPE_* */
+	__u8	result;		/* Result of request (in responses only) */
+	/* 2 bytes pad, must be zero (ignore when read) */
+} __aligned(sizeof(u64));
+
+/*
  * Protocol code should only examine the payload and payload_size
  * fields.  All other fields are intended to be private to the
  * operations core code.