[openib-general] DMA mapping abuses in MAD layer

[Roland Dreier]

    Fab> Why not just use inline sends for the special QPs and remove
    Fab> the need to perform any DMA mappings on the send side
    Fab> altogether?

Not all HCAs necessarily support inline sends, so we can't use them in
core code.  In fact, I don't think that even all Mellanox HCAs would
be able to handle big enough inline sends.  Sending a 256-byte MAD
would require a 512-byte WQE to put the payload in inline data, and if
I recall correctly, MT25204 can't handle WQEs that big.

 - R.