IB: Add ib_modify_qp_is_ok() library function

The in-kernel mthca driver contains a table of which attributes are
valid for each queue pair state transition.  It turns out that both
other IB drivers -- ipath and ehca -- which are being prepared for
merging have copied this table, errors and all.

To forestall this code duplication, move this table and the code to
check parameters against it into a midlayer library function,
ib_modify_qp_is_ok().

Signed-off-by: Roland Dreier <rolandd@cisco.com>

include/rdma/ib_verbs.h

@@ -990,6 +990,24 @@ static inline int ib_copy_to_udata(struct ib_udata *udata, void *src, size_t len
 	return copy_to_user(udata->outbuf, src, len) ? -EFAULT : 0;
 }
 
+/**
+ * ib_modify_qp_is_ok - Check that the supplied attribute mask
+ * contains all required attributes and no attributes not allowed for
+ * the given QP state transition.
+ * @cur_state: Current QP state
+ * @next_state: Next QP state
+ * @type: QP type
+ * @mask: Mask of supplied QP attributes
+ *
+ * This function is a helper function that a low-level driver's
+ * modify_qp method can use to validate the consumer's input.  It
+ * checks that cur_state and next_state are valid QP states, that a
+ * transition from cur_state to next_state is allowed by the IB spec,
+ * and that the attribute mask supplied is allowed for the transition.
+ */
+int ib_modify_qp_is_ok(enum ib_qp_state cur_state, enum ib_qp_state next_state,
+		       enum ib_qp_type type, enum ib_qp_attr_mask mask);
+
 int ib_register_event_handler  (struct ib_event_handler *event_handler);
 int ib_unregister_event_handler(struct ib_event_handler *event_handler);
 void ib_dispatch_event(struct ib_event *event);