Re: [dpdk-dev] [PATCH v1 0/7] Flow API helpers enhancements

[Adrien Mazarguil <adrien.mazarguil@6wind.com>]

On Tue, Oct 10, 2017 at 07:05:30PM +0100, Ferruh Yigit wrote:
> On 10/6/2017 9:05 AM, Adrien Mazarguil wrote:
> > On Fri, Oct 06, 2017 at 02:13:14AM +0100, Ferruh Yigit wrote:
> >> On 10/5/2017 10:49 AM, Adrien Mazarguil wrote:
> >>> This series brings enhancements to various rte_flow helpers:
> >>>
> >>> - Allow applications to use rte_flow_error_set() by making it part of the
> >>>   public interface and documenting it as such.
> >>>
> >>> - Address rte_flow_copy()'s limitations by replacing it with the more
> >>>   versatile rte_flow_conv(). This new function allows retrieving other
> >>>   properties such as item/action names, enabling testpmd to finally use it
> >>>   and get rid of duplicated code.
> >>>
> >>> - Add a script (gen-rte_flow_conv-h.sh) to help with generating the
> >>>   resources used by rte_flow_conv(). Developers should run it when adding or
> >>>   modifying pattern items or actions (done as part of this series to add the
> >>>   missing "fuzzy" pattern item).
> >>>
> >>> - Future plans for rte_flow_conv() include translating error codes to
> >>>   human-readable messages, so applications do not have to make their own.
> >>>
> >>> All these changes address concerns raised a couple of months ago [1]. Work
> >>> on these patches actually started at the time but I was unable to complete
> >>> and clean them up until recently.
> >>>
> >>> [1] http://dpdk.org/ml/archives/dev/2017-July/070492.html
> >>>
> >>> Adrien Mazarguil (7):
> >>>   ethdev: expose flow API error helper
> >>>   ethdev: replace flow API object copy function
> >>>   ethdev: add flow API item/action name conversion
> >>>   app/testpmd: rely on flow API conversion function
> >>>   ethdev: enhance flow API item/action descriptions
> >>>   ethdev: generate flow API conversion header
> >>>   ethdev: update flow API conversion header
> >>
> >> Hi Adrien,
> >>
> >> This received too late for this release cycle, and changes in rte_flow
> >> library may effect PMDs.
> >>
> >> I suggest deferring the set to next release, what do you think?
> > 
> > Hi Ferruh,
> > 
> > My opinion as the author (since you're asking :) is that it would be nice to
> > have it in this release assuming reviewers don't find blocker issues with
> > it.
> 
> Review part may be the problem, since this is very short notice before
> release, relevant parties may not review this on time.
> And they will be right to not expect a new feature like this after
> proposal deadline.

Yes, I generally agree with that.

> > To summarize the changes from a PMD standpoint:
> > 
> > - rte_flow_error() (previously not public) switching from positive to
> >   negative return value like the other rte_flow_*() functions. The only PMDs
> >   relying on its return value so far are mlx4 and tap.
> > 
> > - rte_flow_copy() disappearing. This function was temporary pending a better
> >   solution, and so far is only used by fail-safe PMD (modified as part of
> >   this series). Besides fail-safe, PMDs did not a have a use case for this
> >   function.
> 
> Although you update all rte_flow_copy() usage in the DPDK, this is
> public API right, and technically a user code may be using this, can we
> remove this without notice?

Right, actually rte_flow_copy() was missing the EXPERIMENTAL tag. It's been
present for a single release and wasn't documented as being officially part
of the public rte_flow interface, unlike this series with rte_flow_conv().

For various reasons including its lack of flexibility (enforced by the
struct rte_flow_desc format), I honestly believe rte_flow_copy() is only
presently used by the fail-safe PMD. I may be wrong, and in the case of
complaints the plan is to re-add rte_flow_copy() as a wrapper to
rte_flow_conv() later as a standard maintenance fix.

> > These patches were originally targeted at 17.08, and since the "fuzzy" item
> > is missing from rte_flow_copy() (GTP/GTPU/GTPC are now also missing by the
> > way) and there is currently a lot of redundancy between this function and
> > testpmd's internals, I thought it would be a good time to have everything in
> > a single place. I was also considering using rte_flow_conv() in upcoming
> > mlx4 patches in case it was included.
> > 
> > So here's my suggestion: I can track all rte_flow-related changes in PMDs
> > and in rte_flow itself and update this series accordingly until things have
> > settled (e.g. I'll re-submit to rebase and include GTP). Once applied, I
> > will check all new code that relies on these two functions and update it if
> > necessary until the release. How about that?
> 
> I have no concern that you will do the necessary updates, and agreed it
> is good to get updates to help maintenance, and it would be nice to have
> these in the this LTS release.
> 
> After above said, API changes one week before integration deadline, a
> new script and make target for automated header file, I am a little
> scared :), I will be much relieved to get this in the beginning of the
> next release cycle.

I can drop the script from this series to speed up inclusion if it there's
any concern about it. It's only a helper to update rte_flow_conv.h after
modifying rte_flow.h, I thought it could be useful to anyone, hence I've
included it but it's pretty much optional.

> I would like to see more comment on this, specially from PMD maintainers.

Me too. I don't even mind negative ones!

Here's what I plan to do regardless, seeing most concerns so far are with
rte_flow_copy()/rte_flow_conv():

- Whether this series is included for 17.11 or later, a v2 is already
  necessary.

- I will drop the rte_flow_error() change to submit it instead along another
  upcoming series for mlx4 where it's the most needed.

- We'll then continue to discuss rte_flow_conv() as a something nice to have
  but not super urgent to integrate and I'll keep trying to convince
  everyone it's safe enough.

- Once it becomes clear there's no way to have it for 17.11, I'll update
  this series as a somewhat late deprecation notice for rte_flow_copy().

Sounds good?

-- 
Adrien Mazarguil
6WIND