[P4-discuss] Doubts after my first try on p4lang

Yousong Zhou yszhou4tech at gmail.com
Thu Jun 22 21:53:17 EDT 2017

Hi, I have a few doubts and encountered several issues that I'd like
to share with the list in the hope that it may help the project.

I think there is a typo in the description of "Figure 10" of p4-16
spec.  It says "Parameters are bound by the data plane", but it says
also in a few other places that directionless parameters are to be
bound the control plane though I still have no clue who the control
plane is supposed to be and how that is actually done, but this is
another issue...

The other thing that doubts me is about the versioning scheme of
p4lang specs.  Currently I see we have p4-16 as the current release
and p4-14 as the previous release.  But

 - p4-14 has version 1.0.4 > version 1.0.0 of p4-16
 - p4-14 has date May 24, 2017 > May 22, 2017 of p4-16

How is this so and I am curious about what the suffixes -14 and -16
are for?  Maybe preparing a changelog can also help in the new release
of a spec

After reading "Example: a very simple switch" of p4-16, I thought then
I should now have a fairly good working understanding of p4lang, but
later when trying p4lang/tutorials I got struck with the impression
that the lang must have changed significantly somehow....  The content
and structure of .p4 files there are different and it took me a while
to find core.p4 in p4lang/p4c which I do not know its relationship to
bmv2 and p4c-bm...

I have a few minor patches [1] while preparing and trying the
copy-to-cpu example in tutorials.  But I am not sure whether those 3
repos (bmv2, p4c-bm, tutorials) are still relevant or are they also to
be deprecated

 [1] https://github.com/yousong/build-scripts/commit/91282702eafe1aa21a41d056ab00fda204c20d59#diff-ee344f88969e36b33e3d0479ee719d22R29


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