Re: [ptxdist] [PATCH] libgpiod: select HOST_SYSTEM_PYTHON3_DEV for Python bindings

[Markus Heidelberg via ptxdist <ptxdist@pengutronix.de>]

> On Tue, May 27, 2025 at 11:28:23AM +0000, Markus Heidelberg wrote:
> > On Sun, May 25, 2025 at 03:50:17PM +0200, Michael Olbrich wrote:
> > > On Tue, May 20, 2025 at 02:21:51PM +0200, Markus Heidelberg via ptxdist wrote:
> > > > python3-config has to exist, available in python3-dev Debian package.
> > > > 
> > > > Fixes the following error in libgpiod prepare stage:
> > > > 
> > > >   checking for python3-config... false
> > > >   configure: error: python3-config not found - needed for python bindings
> > > > 
> > > > Signed-off-by: Markus Heidelberg <m.heidelberg@cab.de>
> > > > ---
> > > >  rules/libgpiod.in | 1 +
> > > >  1 file changed, 1 insertion(+)
> > > > 
> > > > diff --git a/rules/libgpiod.in b/rules/libgpiod.in
> > > > index 94bff5164..012223ff1 100644
> > > > --- a/rules/libgpiod.in
> > > > +++ b/rules/libgpiod.in
> > > > @@ -6,6 +6,7 @@ menuconfig LIBGPIOD
> > > >  	select HOST_SYSTEM_PYTHON3
> > > >  	select GCCLIBS_CXX	if LIBGPIOD_CXX
> > > >  	select PYTHON3		if LIBGPIOD_PYTHON3
> > > > +	select HOST_SYSTEM_PYTHON3_DEV	if LIBGPIOD_PYTHON3
> > > 
> > > No, this is wrong. The python3-config should come from the Python we use to
> > > build stuff for the target, so host-python/python.
> > > 
> > > We do some hacky stuff to combine the host-python binary with target python
> > > stuff to get a cross python to build stuff. Maybe that needs to be extended
> > > so that libgpiod will find python3-config?
> > 
> > I guess python3-config from sysroot-cross should be used, but there is
> > only python3.13-config. So I wonder whether
> > 
> > A) there is a symlink (or copy) missing:
> >    sysroot-cross/usr/bin/python3-config -> python3.13-config
> > 
> > B) libgpiod's configure.ac has to be patched:
> >    -python3-config
> >    +python3.13-config
> 
> Try adding ac_cv_prog_has_python_config=python3.13-config to
> LIBGPIOD_CONF_ENV. Does that help?

Yes, that helps, libgpiod builds successfully then.

However, finally I had a look into the libgpiod sources and noticed that
python3-config is not used at all. Autotools aren't used anymore to
build the Python bindings since v2:
https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/commit/bindings/python/Makefile.am?id=b7ba732e6a93313d4609c4d3ffb426996bf68d02

Later some Python leftover had been removed from configure.ac, but not
the python3-config check:
https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/commit/?id=8aab09cb23b19799c058f3375afde5f07de03eef

So it would probably be better to just remove the python3-config check.
I'll submit a patch upstream and when accepted submit it to PTXdist.

Markus