Re: [PATCH v3] ethdev: deprecate header fields and metadata flow actions

[Thomas Monjalon <thomas@monjalon.net>]

24/11/2021 17:37, Slava Ovsiienko:
> From: Ori Kam <orika@nvidia.com>
> > From: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
> > >  Action: ``OF_SET_MPLS_TTL``
> > >  ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > > +This action is deprecated. Consider `Action: MODIFY_FIELD`_.
> > >
> > 
> > Since no PMD support this action why set reference to MODIFY_FIELD_?
> > Same for all unsupported actions.
> 
> There are some references to this action in PMDs (for example bnxt),
> but the ENOTSUP returned. I.e., action is in source code, but actually
> not supported. Hence (due to this and in general), we can't just occasionally
> remove existing actions, we should deprecate these ones first.
> Other point - if someone will decide to implement support for this
> action in his/her PMD - the deprecation notice will point out the right way -
> "consider MODIFY_FIELD."
> 
> > 
> > >  Implements ``OFPAT_SET_MPLS_TTL`` ("MPLS TTL") as defined by the
> > > `OpenFlow  Switch Specification`_.
> > > @@ -2254,6 +2255,7 @@ Switch Specification`_.
> > >
> [..snip..]
> > 
> > If no PMD support this why do we want to add it to the modify_field?
> > Same for all of the unsupported actions.
> As I said above - we just propose to consider MODIFY_FIELD actions
> if someone has intention to implement deprecated OFPAT_SET_MPLS_TTL.

It was an API, we must guide the API reader in the right direction.
BTW, it can be implemented in a driver which is not yet upstream.