[openib-general] Re: libmthca problem: max_inline_size

[Roland Dreier]

    > 2. Return the actual QP capability in create qp command.
    >    This is an ABI change, although the library can be made to work in a
    >    backward compatible way.
    > 3. Add a command (device specific) to query the max descriptor size supported
    >    by the HCA (returned by query dev lim) and calculate max_inline_size
    >    based on that.
    >    Again, this is an ABI change.

    > I am inclining towards the second option (2.) since this way the
    > resulting capability calculations will be all in one place in kernel.

I think we need a combination of 2. and 3. because the WQE shifts and
buffers from userspace need to match up with the kernel.

For 3. there's no need to a completely new command.  We could return
extra device-dependent values from the GET_CONTEXT command, or even
just add some sysfs attributes to the mthca device (similar to the
fw_ver attribute).

    > There's a similiar problem in mthca_arbel_post_send where the
    > inline data size is checked against the expression

    > 	int max_size = (1 << qp->sq.wqe_shift) - sizeof *seg - size * 16;

    > I would imagine the way to fix that is to add a max_inline_size field
    > to the mthca_qp structure and is that instead of 1 << qp->sq.wqe_shift.

Yes, that makes sense.

 - R.