[PATCH v2 1/2] build: clarify configuration without IOVA field in mbuf

[Thomas Monjalon]

09/03/2023 14:10, Bruce Richardson:
> On Thu, Mar 09, 2023 at 01:12:51PM +0100, Thomas Monjalon wrote:
> > 09/03/2023 12:23, fengchengwen:
> > > On 2023/3/9 15:29, Thomas Monjalon wrote:
> > > > 09/03/2023 02:43, fengchengwen:
> > > >> On 2023/3/7 0:13, Thomas Monjalon wrote:
> > > >>> --- a/doc/guides/rel_notes/release_22_11.rst
> > > >>> +++ b/doc/guides/rel_notes/release_22_11.rst
> > > >>> @@ -504,7 +504,7 @@ ABI Changes
> > > >>>    ``rte-worker-<lcore_id>`` so that DPDK can accommodate lcores higher than 99.
> > > >>>  
> > > >>>  * mbuf: Replaced ``buf_iova`` field with ``next`` field and added a new field
> > > >>> -  ``dynfield2`` at its place in second cacheline if ``RTE_IOVA_AS_PA`` is 0.
> > > >>> +  ``dynfield2`` at its place in second cacheline if ``RTE_IOVA_IN_MBUF`` is 0.
> > > >>
> > > >> Should add to release 23.03 rst.
> > > > 
> > > > Yes we could add a note in API changes.
> > > > 
> > > >> The original 22.11 still have RTE_IOVA_AS_PA definition.
> > > > 
> > > > Yes it was not a good idea to rename in the release notes.
> > > > 
> > > >>> -if dpdk_conf.get('RTE_IOVA_AS_PA') == 0
> > > >>> -    build = false
> > > >>> -    reason = 'driver does not support disabling IOVA as PA mode'
> > > >>> +if not get_option('enable_iova_as_pa')
> > > >>>      subdir_done()
> > > >>>  endif
> > > >>
> > > >> Suggest keep original, and replace RTE_IOVA_AS_PA with RTE_IOVA_IN_MBUF:
> > > >> if dpdk_conf.get('RTE_IOVA_IN_MBUF') == 0
> > > >>      subdir_done()
> > > >> endif
> > > > 
> > > > Why testing the C macro in Meson?
> > > > It looks simpler to check the Meson option in Meson.
> > > 
> > > The macro was create in meson.build: config/meson.build:319:dpdk_conf.set10('RTE_IOVA_AS_PA', get_option('enable_iova_as_pa'))
> > > It can be regarded as alias of enable_iova_as_pa.
> > 
> > It is not strictly an alias, because it can be overriden via CFLAGS.
> > 
> > > This commit was mainly used to improve comprehensibility. so we should limit the 'enable_iova_as_pa' usage scope.
> > > and the 'if dpdk_conf.get('RTE_IOVA_IN_MBUF') == 0' is more comprehensibility than 'if not get_option('enable_iova_as_pa')'
> > 
> > To me, using Meson option in Meson files is more obvious.
> > 
> > Bruce, what do you think?
> > 
> 
> I'm not sure it matters much! However, I think of the two, using the
> reference to IOVA_IN_MBUF is clearer. It also allows the same terminology
> to be used in meson and C files. If we don't want to do a dpdk_conf lookup,
> we can always assign the option to a meson variable called iova_in_mbuf.

OK I'll query the C macro in the Meson files.