[openib-general] IPOIB NAPI

[Michael S. Tsirkin]

>  > An API idea:
>  > how about instead testing missed_events, we add a flag:
>  > 
>  > IB_CQ_TEST (or a longer name IB_CQ_REPORT_MISSED_EVENTS?)
>  > and change ib_req_notify_cq to return int which will keep
>  > the missed_events value, only if this flag is set?
>  > 
>  > This has 2 advatages
>  > - Less churn updating all users to new API - they just ignore return value -
>  >   and still almost no overhead for them as they don't set IB_CQ_TEST
>  > - For all users we have to push less values on stack - note compiler can't
>  >   get rid of them as we are calling function through a pointer
>  > - For users that do
>  >   missed_events = ib_req_notify_cq(priv->cq, IB_CQ_NEXT_COMP | IB_CQ_TEST)
>  >   we get the result in register.
> 
> Yes, I like this.  So ib_req_notify_cq() gets a return value that is
> negative if an error occurred, 0 if everything is fine, or positive if
> a missed event might have happened.
> 
> I think I prefer the longer name IB_CQ_REPORT_MISSED_EVENTS -- at
> least there's a chance at guessing what it means even if you don't
> read the documentation.

By the way, how about extending the userspace API in a similiar
fashion?

missed_events = ibv_req_notify_cq(priv->cq, IBV_CQ_NEXT_COMP |
				  IBV_CQ_REPORT_MISSED_EVENTS)


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MST