[ofw] API breakage in trunk

[Sean Hefty]

>We can now add new fields at the end of the structure for version = 1, like
>
>	// for LLE
>	enum rdma_transport_type[MAX_PORT_NUM]	transport;
>
>	// for vendor specific info
>	enum vendor_info_type		vendor_info;
>	union {
>		uplink_info_t		mlnx_vendor_info;
// for
>Mellanox
>	};
>
>It doesn't break the backward compability as far as I see.

Keep in mind that existing applications do not check or set this field.  So it's
not clear how an app uses it.

>What do you think ?
>
>Implementation note:
> The structure ib_ca_attr_t contains a variable part, consisting of two arrays
>(page_sizes and port_attrs).
> Their start is shown by pointers p_page_size and p_port_attr.
> In version 1 these arrays will be placed *after* new fields and the pointers
>will be appropriately adjusted.

I don't see any reason why ib_ca_attr_t can't just be extended, with all new
fields at the end of the structure.  It's the per port data that has issues.

For the kernel, I don't see problems with any of the changes, but breaking user
space apps is different.  Also, winverbs has versioning built into its
interfaces, so exposing this sort of change through that interface is easier to
manage, if you're willing to start deprecating other interfaces.