[openib-general] Re: [RFC] [PATCH] user_mad: Support RMPP on send side

[Roland Dreier]

    Hal> It appears to me that there is nothing that enforces the man
    Hal> page behavior above in Linux so this is a "convention". Is
    Hal> this something we can take advantage of or do we need to
    Hal> require the additional call to get the buffer length ?

Something I was thinking a little while ago was that the character
device interface for userspace MADs might have been a mistake.  Having
a new datagram socket family would solve this problem quite nicely --
a consumer could pass MSG_PEEK and/or MSG_TRUNC to recv() to get the
true length of a datagram.  However it's a little tricky to see a
really clean way for userspace to use this to handle arbitrary sized
RMPP receives.

 - R.