Re: [dpdk-dev] [PATCH 2/4] doc: specify RTE flow create behaviour

[Ori Kam <orika@nvidia.com>]

Hi

> -----Original Message-----
> From: Ajit Khaparde <ajit.khaparde@broadcom.com>
> Sent: Monday, July 26, 2021 6:07 AM
> 
> On Wed, Jul 21, 2021 at 11:16 AM Stephen Hemminger
> <stephen@networkplumber.org> wrote:
> >
> > On Wed, 21 Jul 2021 17:58:14 +0200
> > Martin Havlik <xhavli56@stud.fit.vutbr.cz> wrote:
> >
> > > The ability to create RTE flow rules, depending on
> > > port status, can and does differ between PMDs.
> > > Now the doc reflects that.
> > >
> > > Signed-off-by: Martin Havlik <xhavli56@stud.fit.vutbr.cz>
> > > ---
> > >  doc/guides/prog_guide/rte_flow.rst | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > >
> > > diff --git a/doc/guides/prog_guide/rte_flow.rst
> b/doc/guides/prog_guide/rte_flow.rst
> > > index 2b42d5ec8c..2988e3328a 100644
> > > --- a/doc/guides/prog_guide/rte_flow.rst
> > > +++ b/doc/guides/prog_guide/rte_flow.rst
> > > @@ -3097,6 +3097,10 @@ actually created and a handle returned.
> > >                     const struct rte_flow_action *actions[],
> > >                     struct rte_flow_error *error);
> > >
> > > +The ability to create a flow rule may depend on the status
> (started/stopped)
> > > +of the port for which the rule is being created. This behaviour is
> > > +PMD specific. Seek relevant PMD documentation for details.
> >
> > Any PMD specific behavior in DPDK is an anathema to application
> developers
> > and should be considered a design flaw!
> But it is better to be clear about the behavior.
> Drivers and their underlying devices may need certain resources to be
> initialized before flows could be created. There may be some drivers
> who do not need that.
> Specifying ports to be started would cover both the cases.
> 
> Maybe then we can say that "some drivers may _not_ need the port to be
> started. Check PMD specific documentation".

I don't like the negative approach, if a driver doesn't have any issues with something
it doesn't need to say it support this, the driver may say if it wants to emphasize
but this shouldn't be the default.
I prefer the original suggestion, maybe we can add device cap for this, just like
if a the PMD allows modifying queues after start.

Best
Ori