[U-Boot] python3 support for pylibfdt

[Tom Rini <trini@konsulko.com>]

On Fri, Jun 28, 2019 at 01:38:01PM +0100, Peter Robinson wrote:
> > > > > With the EOL of python2 soon I've been looking at the Fedora U-Boot
> > > > > builds to see what it would take to move over to python3. There's a
> > > > > couple of issues building the bundled pylibfdt, the first is the
> > > > > Makefile hard codes python2, the second is that the generated
> > > > > libfdt_wrap.c doesn't seem to find the python3 version of Python.h
> > > > > (errors below).
> > > > >
> > > > > It seems upstream now supports building pylibfdt with dtc 1.5.0 but I
> > > > > couldn't quite work out how this fits into the U-Boot bundled version.
> > > > > Is there plans to be able to support pylibfdt with python3?
> > > >
> > > > Sounds like we need to run the normal kernel script to re-sync with
> > > > upstream?  Thanks!
> > >
> > > Seems reasonable, I'll keep an eye out for a patch series to test,
> > > it's quite straight forward to test from my PoV.
> >
> > It won't be any time soon, sadly.  Updating to the same dtc in the
> > kernel (so just v1.4.7+) causes both massive amount of new device tree
> > warnings as well as several fail to link due to size growth problems.
> 
> I'm guessing the size problem is due to an increase in size of where
> libfdt is linked in and not due to pylibfdt. Would it make sense to
> have a feature branch with the rebase to make it easier to test/fix
> the issues? And rebasing some DT to the current kernel versions should
> fix up a bunch of the DT problems?

The size growth is due to the C side growing, yes.  Some of it is the
safety checking I warned about back at the time and the rest of it is
just general growth (U-Boot is guilty of that all the time, so I can't
really complain about some other project growing slightly).

Rebasing to the current kernel version adds a bunch of DT problems, some
of which I hope would be fixed by re-syncing the base DT at least.

> Fedora, as are many other distros, is actively retiring python2 due to
> it's upcoming EOL ~ 6 months from now. I've had to already rescue a
> couple of python2 packages to keep U-Boot building, there's an
> intention to actively remove python2 in Fedora 32 (scheduled for May
> 2020) which means anything post U-Boot 2019.10 (the version we're
> aiming for in F-31) will start to cause me big problems.
> 
> Maybe we could add this to migration plans like any of the DM subsytems?

So, looking again, the problem is that upstream, pylibfdt/setup.py is
still using python2.  So while a resync with upstream dtc might be good,
it won't solve this issue.  I'm not even sure why it doesn't work with
Python3, other than that in January we added a patch to ensure we used
Python2 and not 3.

Simon, I don't see your series that updated a bunch of stuff to work
with Python 3 in master, but it's listed as Accepted in patchwork, do
you know what happened?  Thanks!

-- 
Tom
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