[dpdk-stable] [dpdk-dev] Re: [PATCH] devtools: skip the symbol check when map file under drivers

[Jerin Jacob Kollanukkaran]

> -----Original Message-----
> From: Neil Horman <nhorman at tuxdriver.com>
> Sent: Wednesday, May 22, 2019 6:43 PM
> To: Jerin Jacob Kollanukkaran <jerinj at marvell.com>
> Cc: Bruce Richardson <bruce.richardson at intel.com>; dev at dpdk.org;
> thomas at monjalon.net; stable at dpdk.org
> Subject: [EXT] Re: [dpdk-dev] Re: [PATCH] devtools: skip the symbol check
> when map file under drivers
> 
> External Email
> 
> ----------------------------------------------------------------------
> On Wed, May 22, 2019 at 11:54:13AM +0000, Jerin Jacob Kollanukkaran
> wrote:
> > > -----Original Message-----
> > > From: Bruce Richardson <bruce.richardson at intel.com>
> > > Sent: Wednesday, May 22, 2019 4:21 PM
> > > To: Jerin Jacob Kollanukkaran <jerinj at marvell.com>
> > > Cc: Neil Horman <nhorman at tuxdriver.com>; dev at dpdk.org;
> > > thomas at monjalon.net; stable at dpdk.org
> > > Subject: Re: [dpdk-dev] [EXT] Re: [PATCH] devtools: skip the symbol
> > > check when map file under drivers
> > >
> > > > > Sorry, but I'm not ok with this, because many of our DPDK PMDs
> > > > > have functions that get exported which are meant to be called by
> > > > > applications directly.  The
> > > >
> > > > OK. Just to update my knowledge, Should those API needs to go
> > > > through ABI/API depreciation process?
> > > >
> > > > Actually, I am concerned about the APIs, which is called between
> > > > drviers not the application. For example,
> > > > drivers/common/dpaax/rte_common_dpaax_version.map
> > > >
> > > > it is not interface to application rather it is for intra driver case.
> > > > I think, I can change my logic to Skip the symbols which NOT
> > > > starting with
> > > rte_.
> > > > Agree?
> > > >
> > > > Context:
> > > > I am adding a new driver/common/octeontx2 directory and it has
> > > > some API which Needs to shared between drivers not to the
> > > > application. For me, it does not make sense to go through any ABI
> process in such case.
> > > >
> > > >
> > > Maybe not, but other drivers will have APIs designed for apps to
> > > call directly - some NIC drivers have them, and I suspect that
> > > rawdev drivers will need them a lot. Therefore, it's best to have
> > > the drivers directory scanned by our tooling.
> >
> > Agreed. But all of those API  which called directly called from
> > application is starts with rte_ symbol. How about skipping the symbols
> > which is NOT start with rte_*
> > example:
> > drivers/common/octeontx/rte_common_octeontx_version.map
> > drivers/common/dpaax/rte_common_dpaax_version.map
> >
> 
> No, that won't work.  If you export a function, it doesn't matter if its named
> rte_* or not.  Its accessible from any library/application that cares to call it,

IMO, The name prefix matters. The rte_* should denote it a DPDK API and application
suppose to use it.

I don't think, giving experimental status to intra driver API helps anyone, neither driver nor
application.

If you think strongly that experimental needs to be added for intra driver APIs then I can add that.
 

> and so you have a responsibility to keep it stable for those users.
> 
> Currently the way we have around that is the use of the __rte_experimental
> tag.
> Adding that tag to an exported function marks it as being unstable, and while
> you can use it, it will generate a build time warning about its use, unless you
> define ALLOW_EXPERIMENTAL_API.  You could use that, understanding that
> in-tree drivers could use it safely, as you should always be keeping the API in
> sync with its users, but thats not quite what you want I don't think.
> 
> Another solution (allbeit a slightly risky one), would be to bifurcate your
> header files into a public and private version, with the private version
> prototyping your driver-only functions properly, and the public version
> aliasing them such that they generate a build time error indicating those
> functions aren't available for public use (you can use the gcc static_assert
> macro I believe).  Users could circumvent it by pulling the private header out
> of the build, or just prototyping the functions themselves, but at that point a
> user is asking for trouble anyway
> 
> Neil