Re: [dpdk-dev] [PATCH v2 1/4] ethdev: introduce indirect action APIs

[Thomas Monjalon <thomas@monjalon.net>]

15/04/2021 15:55, Andrew Rybchenko:
> On 4/10/21 5:03 PM, Bing Zhao wrote:
> > Right now, rte_flow_shared_action_* APIs are used for some shared
> > actions, like RSS, count. The shared action should be created before
> > using it inside a flow. These shared actions sometimes are not
> > really shared but just some indirect actions decoupled from a flow.
> >
> > The new functions rte_flow_action_handle_* are added to replace
> > the current shared functions rte_flow_shared_action_*.
> >
> > There are two types of flow actions:
> > 1. the direct (normal) actions that could be created and stored
> >    within a flow rule. Such action is tied to its flow rule and
> >    cannot be reused.
> > 2. the indirect action, in the past, named shared_action. It is
> >    created from a direct actioni, like count or rss, and then used
> >    in the flow rules with an object handle. The PMD will take care
> >    of the retrieve from indirect action to the direct action
> >    when it is referenced.
> >
> > The indirect action is accessed (update / query) w/o any flow rule,
> > just via the action object handle. For example, when querying or
> > resetting a counter, it could be done out of any flow using this
> > counter, but only the handle of the counter action object is
> > required.
> > The indirect action object could be shared by different flows or
> > used by a single flow, depending on the direct action type and
> > the real-life requirements.
> > The handle of an indirect action object is opaque and defined in
> > each driver and possibly different per direct action type.
> >
> > The old name "shared" is improper in a sense and should be replaced.
> >
> > All the command lines in testpmd application with "shared_action*"
> > are replaced with "indirect_action*".
> >
> > The parameter of "update" interface is also changed. A general
> > pointer will replace the rte_flow_action struct pointer due to the
> > facts:
> > 1. Some action may not support fields updating. In the example of a
> >    counter, the only "update" supported should be the reset. So
> >    passing a rte_flow_action struct pointer is meaningless and
> >    there is even no such corresponding action struct. What's more,
> >    if more than one operations should be supported, for some other
> >    action, such pointer parameter may not meet the need.
> > 2. Some action may need conditional or partial update, the current
> >    parameter will not provide the ability to indicate which part(s)
> >    to update.
> >    For different types of indirect action objects, the pointer could
> >    either be the same of rte_flow_action* struct - in order not to
> >    break the current driver implementation, or some wrapper
> >    structures with bits as masks to indicate which part to be
> >    updated, depending on real needs of the corresponding direct
> >    action. For different direct actions, the structures of indirect
> >    action objects updating will be different.
> >
> > All the underlayer PMD callbacks will be moved to these new APIs.
> >
> > The RTE_FLOW_ACTION_TYPE_SHARED is kept for now in order not to
> > break the ABI. All the implementations are changed by using
> > RTE_FLOW_ACTION_TYPE_INDIRECT.
> >
> > Signed-off-by: Bing Zhao <bingz@nvidia.com>
> 
> Just for the record. I still dislike renaming since "shared" highlights
> purpose (what is definitely better), but "indirect" is just a technical
> detail on how it is done.

The difference is that indirect action is not only for sharing.
It allows manipulating an action as an object.
Action object is inserted in flow rules through the indirect action.
Does it make it clearer?