[ofa-general] Re: Incorrect max_sge reported in mthca device query

[Sean Hefty]

>The challenge with the current query/request method is that as we've
>discussed the advertised max may not work. What makes the adjust/retry
>unworkable is that you don't know which of the advertised maxes caused
>the request to fail. So when you retry, which qp_attr do you adjust? The
>send sge? The recv sge? The qp depth?
>
>So what I'm proposing, and I think is similar if not identical to what
>other folks have talked about is having an interface that treats the
>qp_attr values as requested-sizes that can be adjusted by the provider.
>So for example, if I ask for a send_sge of 30, but you can only do 28,
>you give me 28 and adjust the qp_attr structure so that I know what I
>got. This would allow me to perform a predictable sequence of 1. query,
>2. request, 3. adjust in my code.

If the send sge/recv sge/qp depth/etc. aren't independent though, this pushes
the problem and policy decision down to the provider.  I can't think of an easy
solution to this.

- Sean