IB/core: Add ability for drivers to report an alternate MAD size.

Add max MAD size to the device immutable data set and have all drivers that
support MADs report the current IB MAD size (IB_MGMT_MAD_SIZE) to the core.

Verify MAD size data in both the MAD core and when reading the immutable data.

OPA drivers will report alternate MAD sizes in subsequent patches.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

include/rdma/ib_verbs.h

@@ -1534,6 +1534,7 @@ struct ib_port_immutable {
 	int                           pkey_tbl_len;
 	int                           gid_tbl_len;
 	u32                           core_cap_flags;
+	u32                           max_mad_size;
 };
 
 struct ib_device {
@@ -2052,6 +2053,23 @@ static inline bool rdma_cap_read_multi_sge(struct ib_device *device,
 	return !(device->port_immutable[port_num].core_cap_flags & RDMA_CORE_CAP_PROT_IWARP);
 }
 
+/**
+ * rdma_max_mad_size - Return the max MAD size required by this RDMA Port.
+ *
+ * @device: Device
+ * @port_num: Port number
+ *
+ * This MAD size includes the MAD headers and MAD payload.  No other headers
+ * are included.
+ *
+ * Return the max MAD size required by the Port.  Will return 0 if the port
+ * does not support MADs
+ */
+static inline size_t rdma_max_mad_size(const struct ib_device *device, u8 port_num)
+{
+	return device->port_immutable[port_num].max_mad_size;
+}
+
 int ib_query_gid(struct ib_device *device,
 		 u8 port_num, int index, union ib_gid *gid);