greybus: enforce non-zero operation type requirement

The operation type 0x00 is reserved as an explicitly invalid
operation type in all protocols.  Enforce this.

Add a check for callers who erroneously have the RESPONSE message
type flag set in the operation type passed in gb_operation_create().
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/staging/greybus/operation.c

@@ -455,10 +455,23 @@ gb_operation_create_common(struct gb_connection *connection, bool outgoing,
 	return NULL;
 }
 
+/*
+ * Create a new operation associated with the given connection.  The
+ * request and response sizes provided are the number of bytes
+ * required to hold the request/response payload only.  Both of
+ * these are allowed to be 0.  Note that 0x00 is reserved as an
+ * invalid operation type for all protocols, and this is enforced
+ * here.
+ */
 struct gb_operation *gb_operation_create(struct gb_connection *connection,
 					u8 type, size_t request_size,
 					size_t response_size)
 {
+	if (WARN_ON_ONCE(!type))
+		return NULL;
+	if (WARN_ON_ONCE(type & GB_OPERATION_TYPE_RESPONSE))
+		type &= ~GB_OPERATION_TYPE_RESPONSE;
+
 	return gb_operation_create_common(connection, true, type,
 					request_size, response_size);
 }