[dpdk-dev] [PATCHv4 5/5] doc: Add ABI __experimental tag documentation

Neil Horman nhorman at tuxdriver.com
Sat Jan 13 01:28:40 CET 2018


On Fri, Jan 12, 2018 at 03:55:10PM +0000, Ferruh Yigit wrote:
> On 1/12/2018 2:37 PM, Neil Horman wrote:
> > On Fri, Jan 12, 2018 at 11:50:12AM +0000, Ferruh Yigit wrote:
> >> On 1/11/2018 9:29 PM, Neil Horman wrote:
> >>> On Thu, Jan 11, 2018 at 08:06:48PM +0000, Ferruh Yigit wrote:
> >>>> On 12/13/2017 3:17 PM, Neil Horman wrote:
> >>>>> Document the need to add the __experimental tag to appropriate functions
> >>>>>
> >>>>> Signed-off-by: Neil Horman <nhorman at tuxdriver.com>
> >>>>> CC: Thomas Monjalon <thomas at monjalon.net>
> >>>>> CC: "Mcnamara, John" <john.mcnamara at intel.com>
> >>>>> CC: Bruce Richardson <bruce.richardson at intel.com>
> >>
> >> <...>
> >>
> >>>>>  automatically marked as ``experimental`` to allow for a period of stabilization>>>  before they become part of a tracked ABI.
> >>
> >> Full sentences for above statement:
> >> "
> >> Since changes to APIs are most likely immediately after their introduction, as
> >> users begin to take advantage of those new APIs and start finding issues with
> >> them, new DPDK APIs will be automatically marked as experimental to allow for a
> >> period of stabilization before they become part of a tracked ABI.
> >> "
> >>
> >> This part is not related to this patchset, but it will be hard to maintain above
> >> behavior, "automatically marked" is not automatic now and moving them to stable
> >> after one release is also not automatic. Do you have any suggestion on how to
> >> manage this, do you think can your script be expanded to cover these checks?
> >>
> > 
> > I would make the argument that this was never the case, but rather a statement
> > of principle.  I assert that because I can find no mechanism anywhere in our
> > build system that 'automatically' documented or marked a new API as experimental
> > (please correct me if I'm wrong here).  I think this was more meant to be a
> > directive to developers to do whatever coding was needed to preform such
> > marking/documentation in whatever style/format was current.  E.g. introducers of
> > a new API should document everything as EXPERIMENTAL using the appropriate
> > doxygen tag and version map tag.
> > 
> > In answer to your question, While we might be able to expand my script to check
> > for new API's and ensure they are marked as experimental, I don't think thats
> > the right place to do it, because that script is run at build time, where the
> > state of the tree is transient. A better place to do it would be with a git hook
> > at checkin time, or in the checkpatch script to flag new apis as experimental
> > right before those new API's are comitted.  Though I'm not a huge fan of that
> > either (at least not of the former suggestion).  I say that because I think we
> > need to allow developers the freedom to determine the supported status of any
> > new API that they add.  For example, it seems pretty clear that a new library
> > might want to have its entire API marked as experimental, but someone adding a
> > single new function to an existing API might be confident that the new function
> > is needed and should be immediately supported..
> > 
> > I think the better solution is to define the use of the EXPERIMENTAL tag in the
> > version map as the canonical location to define unstable API functions.  Doing
> > so immediately commits an author to ensuring that the corresponding function
> > definitions are marked with the __experimental tags, which in turn will cause
> > any downstream users to be alerted to the fact that they might be using those
> > API's in their code, so they can take appropriate action.  It still allows for
> > the Documentation to be out of sync, but alerting authors doing development I
> > think is the more important element here, as Documentation can be corrected more
> > easily than code in the field.
> > 
> > Thoughts?
> 
> After this point agree to using EXPERIMENTAL tag in the version map as standard,
> but it will be hard to maintain "API is experimental for first release" without
> help of any automated tool.
> 
I completely agree, in fact I would say it is impossible to do without tooling,
with or without this change.  I think we need to do 1 of 2 things:

1) Add some code to checkpatch.pl to put up a warning if any new apis are added
without marking them as experimental

2) Change the documentation to be a suggestion rather than a requirement.

I'll look into doing (1), but I'm wondering if (2) is the more flexible way to
go. I'm hesitant to enforce the initial marking of new APIs as experimental.
Thoughts?

Neil


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