[PATCH v2] STM32 lwIP addition and CMake support

[Gedare Bloom]

STM is not going to fix their Ultimate Liberty License at this time.
https://github.com/STMicroelectronics/STM32CubeH7/issues/139#issuecomment-890806010

So, we need to avoid using their example codes.

On Wed, Jun 9, 2021 at 12:16 PM Gedare Bloom <gedare at rtems.org> wrote:
>
> I joined the Issue. Thanks for working on this.
>
> On Wed, Jun 9, 2021 at 11:30 AM Robin Müller <robin.mueller.m at gmail.com> wrote:
> >
> > I posted a reply but I think it did not go through. Will post it now.
> >
> > Kind Regards
> > Robin
> >
> > On Wed, 9 Jun 2021 at 18:31, Robin Müller <robin.mueller.m at gmail.com> wrote:
> >>
> >> Hi,
> >>
> >> I received a reply from STM32 about the licensing issues. They requested more specific information about the "vendor device restrictions"  for the HAL code.
> >> The issue is here: https://github.com/STMicroelectronics/STM32CubeH7/issues/139
> >> Can anyone provide more information about this (maybe even directly in the issue) ? I can forward it to them as well. Thanks a lot in advance!
> >>
> >> Kind Regards
> >> Robin
> >>
> >> On Wed, 28 Apr 2021 at 02:45, Chris Johns <chrisj at rtems.org> wrote:
> >>>
> >>> On 28/4/21 2:58 am, Robin Müller wrote:
> >>> > Okay, I can understand that you'd like to have one build system only. We had the
> >>> > same issue with a former Makefile build system and the new CMake system and
> >>> > decided to make the former system obsolete> because maintaining both of them would be too much work
> >>> For RTEMS what we use has been selected for a range of important reasons and the
> >>> rtems-central repo and the qual work highlights the importance of those
> >>> decisions. Waf is a python framework for building software and in rtems.git our
> >>> build system support is written in a clearly defined portable language with
> >>> power helper libraries. We can run code formatters on our build system, have
> >>> unit tests and there is even source level debuggers. We treat the build system
> >>> like any other piece of code we have.
> >>>
> >>> > First thing I  can do is that I split up the patch and extract the CMake
> >>> > specific files. Concerning a clean solution to allow users to use CMake without
> >>> > introducing files like CMakeLists.txt,
> >>> > I am not sure right now. Extracting the information required by CMake would
> >>> > again require scripts to export source files and include paths.
> >>> > The simplest solution would still be a CMakeLists.txt file in the root here
> >>> > which simply sets source files and include paths in the parent scope.
> >>> > which would again be another form of maintenance burden because it still needs
> >>> > to figure out which port sources to add etc.
> >>>
> >>> What about scons, meson, or a plain Makefile for those who just want to use
> >>> make, then there is GNU make and BSD make, the list is large? Do we open the
> >>> repo up so all build systems are welcome? I think we would have to so we are not
> >>> picking favourites.
> >>>
> >>> Who tests these build system files when the package is released? As the person
> >>> who releases RTEMS I do not have the time or capability to do this.
> >>>
> >>> > The rtems-cmake support is able to live without CMakeLists.txt files in RTEMS
> >>> > because the BSP is already compiled at that point. Doing something similar
> >>> > would require a similar process like done in the BSP where rtems-lwip is
> >>> > compiled as a static library for a specific BSP,
> >>> > installed somewhere and then an application can link against it while also
> >>> > including the headers.
> >>>
> >>> I welcome the idea of rtems-cmake to grow a community of those using cmake to
> >>> build RTEMS applications. It is great to see this happening.
> >>>
> >>> > For the RTEMS BSP this is done through provided PKG Config files. It just seems
> >>> > like a lot of effort for a comparatively small library.
> >>> > Maybe someone has a better idea?
> >>>
> >>> I do not have a better solution than PKG config. Most build systems provide
> >>> support so it should be something that can be accommodated.
> >>>
> >>> > I am also not sure if users who are used to CMake would not just do the same
> >>> > thing I did if there are no CMakeLists.txt files present and the
> >>> > library/repository is simple enough:
> >>>
> >>> I would discourage this and maybe not for the reasons you may be thinking of.
> >>> The repo is new and is it is exciting there is work happening on it but in time
> >>> it will become stable and it will be released with RTEMS and this puts it in the
> >>> same configuration management basket as the BSP (kernel) and tools. The RSB can
> >>> build it in a controlled way with reports and you just access it like the BSP.
> >>>
> >>> > Add those themselves in the project root or throughout the repository fork
> >>> > structure. But it's your call of course. Maybe some more (user) opinions would
> >>> > help as well.
> >>>
> >>> I see rtems-cmake providing that role, thank you for it. We have learnt the hard
> >>> way over a few decades to be mindful when adding these things. Strong portable
> >>> eco-system level interfaces are our focus.
> >>>
> >>> Chris