Re: [dpdk-dev] [RFC PATCH 0/5] rework feature enabling macros for compatibility

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 9/16/2020 5:44 PM, Bruce Richardson wrote:
> As flagged previously on-list, there are a number of macros used to specify
> what libs and drivers are enabled in the build which differ from the
> equivalents used with make. This patchset is one possible approach to
> fixing these, but as part of the investigation some issues were hit where
> I'd like additional input to ensure we are ok with the approach taken in
> this set.
> 
> First, a problem statement:
> 
> * While the make build defines generally followed a pattern, there were
>    many instances where the defines were unique. These can be seen in the
>    values defined in patch 4.
> 
> * The NIC PMDs had two separate standards for the defines - some (the
>    physical device drivers) tended to have the _PMD at the end of the
>    macros, while the virtual drivers had it in the middle. Since the
>    majority seemed to go with it at the end, meson chose this option.
>    However, as can be seen from patch 4, a number now need special handling
>    for compatibility

+1 to all X_PMD macros.

> 
> * This "_PMD" at the end made its way into other device classes, such as
>    crypto and event, but it appears that the standard for these classes from
>    make is in fact the opposite. Therefore we have had for the last 2+ years
>    conflicting macros for crypto, compression and event classes.
> 
> * There is also the question of how important compatibility for these
>    macros is, especially since we have had numerous incompatibilities
>    without it being reported before. There is also the issue of the
>    deprecation process for macros, since these are not part of any ABI.
> 
> What's done in this set:
> 
> * Firstly, and missing dependencies on apps or examples had to be fixed,
>    where a dependency was missed because it was never needed due to the code
>    being stripped out because of a missing macro.
> 
> * Secondly, since it is likely that use of the defines from make is more
>    widespread than those from meson, the defines for the crypto, compression
>    and event classes are changed to align with the make values. Just in case
>    though, temporary code is added to drivers/meson.build to redefine the
>    old meson values too, and a deprecation notice is added for these. The
>    hope is that we can then remove this temporary code in the next release,
>    leaving us with just one macro style for each driver class.
> 
> * Thirdly, we add an additional set of backward compatibility macros for
>    the ~30 special-cases, where the meson macro template does not match that
>    defined for make. Again, this is intended to be temporary and a
>    deprecation notice is given for the macros in that file.
 >

Why we need this backward compatibility? The macros are to enable/disable a 
module, so isn't it DPDK internal.
If we enable the macros for new naming convention and update the build system 
and code for new macros, will it affect the end user?

> 
> * Finally, we replace all instances of the old macros in the codebase with
>    the newer versions. While the work done in the first four patches (steps
>    1-3 above) should be ok to backport, this final patch is not suitable for
>    backporting. However, it is relatively simple to produce a new patch for
>    backporting which allow either old or new values to be used in macros.
> 
> 
> Open issues/considerations after this patch:
> 
> * We still have inconsistencies in our driver macro and naming templates.
>    This is just a nice-to-have, but if people are ok with generally having a
>    breakage in our macro defines, we could clean this up a lot further.
>    Notice how 'net', 'regex' and 'vdpa' have '_PMD' at the end, while most
>    others have it before the name. Notice also that many device classes have
>    the class at the end of the template, while bbdev has it in the middle.
> 	$ git grep config_flag_fmt -- drivers/*/meson.build
> 	drivers/baseband/meson.build:config_flag_fmt = 'RTE_LIBRTE_PMD_BBDEV_@0@'
> 	drivers/bus/meson.build:config_flag_fmt = 'RTE_LIBRTE_@0@_BUS'
> 	drivers/common/meson.build:config_flag_fmt = 'RTE_LIBRTE_@0@_COMMON'
> 	drivers/compress/meson.build:config_flag_fmt = 'RTE_LIBRTE_PMD_@0@'
> 	drivers/crypto/meson.build:config_flag_fmt = 'RTE_LIBRTE_PMD_@0@'
> 	drivers/event/meson.build:config_flag_fmt = 'RTE_LIBRTE_PMD_@0@_EVENTDEV'
> 	drivers/mempool/meson.build:config_flag_fmt = 'RTE_LIBRTE_@0@_MEMPOOL'
> 	drivers/net/meson.build:config_flag_fmt = 'RTE_LIBRTE_@0@_PMD'
> 	drivers/raw/meson.build:config_flag_fmt = 'RTE_LIBRTE_PMD_@0@_RAWDEV'
> 	drivers/regex/meson.build:config_flag_fmt = 'RTE_LIBRTE_@0@_PMD'
> 	drivers/vdpa/meson.build:config_flag_fmt = 'RTE_LIBRTE_@0@_PMD'
> 
> * Are we ok to remove the older macros after one release of deprecation, or
>    do we need to wait to next API window.
> 
> * I have not made any changes to the docs for this, since I expect that
>    these macros are already covered by the doc changes in the make removal
>    set.
> 
> Reviews and comments welcome.
> 
> Bruce Richardson (5):
>    app: fix missing dependencies
>    examples/l2fwd-crypto: fix missing dependency
>    meson: fix compatibility with make build defines
>    build: add defines for compatibility with make build
>    build: replace use of old build macros
> 
>   app/test-crypto-perf/meson.build     |   3 +
>   app/test-pmd/cmdline.c               |   8 +-
>   app/test-pmd/meson.build             |  12 +++
>   app/test-pmd/parameters.c            |  12 +--
>   app/test-pmd/testpmd.c               |  24 ++---
>   app/test-pmd/testpmd.h               |   4 +-
>   app/test/meson.build                 |   3 +
>   app/test/test_eal_flags.c            |   4 +-
>   config/meson.build                   |   3 +-
>   config/rte_compatibility_defines.h   | 129 +++++++++++++++++++++++++++
>   config/rte_config.h                  |   1 +
>   doc/guides/rel_notes/deprecation.rst |  17 ++++
>   drivers/compress/meson.build         |   2 +-
>   drivers/crypto/meson.build           |   2 +-
>   drivers/event/meson.build            |   2 +-
>   drivers/meson.build                  |  15 ++++
>   examples/l2fwd-crypto/meson.build    |   3 +
>   17 files changed, 214 insertions(+), 30 deletions(-)
>   create mode 100644 config/rte_compatibility_defines.h
>