Re: [RFC PATCH v2 26/26] config: add computed max queues define for compatibility

[Bruce Richardson <bruce.richardson@intel.com>]

On Wed, Aug 14, 2024 at 08:01:19AM -0700, Stephen Hemminger wrote:
> On Tue, 13 Aug 2024 17:00:03 +0100
> Bruce Richardson <bruce.richards@intel.com> wrote:
> 
> > +.. note::
> > +
> > +   The define ``RTE_MAX_QUEUES_PER_PORT`` is kept for backward compatibility.
> > +   Its value is no longer hard-coded,
> > +   but is set, at configuration time, to the maximum of the configured max Rx and Tx queue values.
> 
> Would rather it just be marked __rte_deprecated because a runtime calculation is going to break
> code that uses this to size arrays at compile time.

"runtime calculation is going to break" -> yep, that's why it's computed at
configuration time using meson, so all C code sees is a hard-coded value.
See commit log message, which calls this out too.

In terms of deprecating the old value, I'd really rather not do so, as I
suspect that this value is likely used in many end-user applications.
While I know according to our policy we could remove this, the cost of
keeping around a backward-compatible version of this seems pretty small and
may avoid breaking lots of end-applications. Then again, we may want to
deprecate it for internal use in DPDK.

/Bruce