GSoC 2020: Implementation of OFW functions

[Niteesh G. S.]

On Thu, May 7, 2020 at 4:07 PM Sebastian Huber <
sebastian.huber at embedded-brains.de> wrote:

> On 07/05/2020 12:28, Niteesh G. S. wrote:
>
> > On Thu, May 7, 2020 at 1:21 PM Sebastian Huber
> > <sebastian.huber at embedded-brains.de
> > <mailto:sebastian.huber at embedded-brains.de>> wrote:
> >
> >     On 07/05/2020 09:35, Niteesh G. S. wrote:
> >
> >     > This is what I was trying to convey in one of the previous mails.
> >     > https://lists.rtems.org/pipermail/devel/2020-May/059717.html
> >     > But in that mail, I was planning to replace KOBJLOOKUP.
> >     > Should I start working on it? From the top of my mind, the
> >     following has
> >     > to be done.
> >     > 1) Import openfirm.c openfirm.h, ofw_fdt.c
> >     > 2) Add ofw_fdt.h since all the functions in ofw_fdt are static.
> >     > Should we also import ofw_if.h? Because that is where OFW_*
> >     functions
> >     > are defined or just add a ofw_rtems_map.h which redefines them,
> >     instead
> >     > of importing ofw_if.h?
> >
> >     The KOBJ stuff in the OFW support enables FreeBSD to have three
> >     different implementations of the OFW API which can be selected at
> >     runtime:
> >
> >     sys/powerpc/ofw/ofw_real.c
> >     sys/dev/ofw/ofw_standard.c
> >     sys/dev/ofw/ofw_fdt.c
> >
> >     In libbsd this is already short cut to the FDT implementation:
> >
> >     #ifndef __rtems__
> >     static ofw_def_t    *ofw_def_impl = NULL;
> >     #else /* __rtems__ */
> >     #define    ofw_def_impl (&ofw_fdt)
> >     #endif /* __rtems__ */
> >
> >     To me this looks like the KOBJ stuff was just used to enable some
> >     sort
> >     of object oriented programming. Do we need this flexibility at
> >     runtime
> >     in RTEMS? I would say no. I would hard wire this to the FDT
> >     implementation. If someone has a problem with it in the future, this
> >     decision can be readdressed.
> >
> >
> > Ok. But what is the neatest way to hardwire this to the FDT
> > implementation?
> > One way as Christian mentioned would be to redefine OFW_* functions to
> > call the functions in ofw_fdt.c directly. Is there any other way?
>
> I would try to replace the function declarations in openfirm.h with
> inline functions which call the ofw_fdt.c functions.
>

Should I proceed with the above method? or should I wait for others
to comment?
If I can proceed, the following is what I will be doing.
1) import openfirm.h and ofw_fdt.c into RTEMS.
2) Add ofw_fdt.h with functions declarations for functions in ofw_fdt.c
3) Add necessary compile-time guards. This would include using __rtems__
preprocessor directive to avoid FreeBSD stuff and change the function
definitions in ofw_fdt.c from static to non-static.
Am I missing something? or is there any other way to do this?
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