[ofw] RE: ndi_modify_qp vs modify_qp

[Sean Hefty]

list copied on response

> Why do we have a separate ndi_modify_qp version?  What is expect back in the
>out buffer?    Is the assumption that it is called from User Mode?

The ndi_modify_qp call supports transitioning a QP from the kernel (more than 1
transition can be done), with the result of those transitions returned to user
space.  In the current HCA libraries, the only data that is returned to the user
space library is the final state of the QP after all transitions have been done.

Basically it allows the kernel to respond to IB CM protocol messages, including
transitioning the QP from INIT to RTR then RTS without multiple user to kernel
transitions.

Control of the out buffer depends on the implementation of the user space
library.  The library just needs to handle the kernel performing QP transitions
without the library being involved after ndi_modify_qp is called.  I believe Fab
added this call, so he may have more information.

- Sean