[openib-general] Re: [PATCH 1 of 2] mthca: qp size calculations

[Michael S. Tsirkin]

Quoting r. Roland Dreier <rolandd at cisco.com>:
> Subject: Re: [PATCH 1 of 2] mthca: qp size calculations
> 
>     Michael> What I had in mind is: lets pad all resp and cmd
>     Michael> structures in userspace (but not in kernel) with some
>     Michael> 0-initialized extra space at the tail.  The time to do it
>     Michael> would be now before we bump the ABI.  Comments?
> 
> I'm not convinced we can do a good enough job of this to make it worth
> it.

Neither do I, it was just an idea to ponder.
Still, people do like upgrading kernels without touching userspace.

> How do we know how much padding to leave?

I guess if we run out of place we can always force the user to
upgrade as we do now, or add a pointer into a sctructure.

> If we're just adding parameters, it's easy to put the compat code in
> userspace anyway.  It's other changes that are hard to deal with.
> 
>  - R.
> 

Well, its your call.

-- 
MST