Re: [Xenomai-help] Re: [Xenomai-core] [ANNOUNCE] Xenomai Example Repository

[Philippe Gerum <rpm@xenomai.org>]

On Fri, 2006-12-01 at 18:22 +0100, Jan Kiszka wrote:
> Wolfgang Grandegger wrote:
> > Jan Kiszka wrote:
> >> Hi,
> >>
> >> the new Xenomai example repository has been created. I don't want to
> >> repeat here what is explained already on the related wiki page, please
> >> have a look at
> >>
> >>     http://www.xenomai.org/index.php/Examples
> >>
> >> Instead, let me sketch what could be done next:
> >>
> >>  o Port existing examples, snippets, demos from ksrc/skins/* over, make
> >>    them compilable and runnable if required.
> >>
> >>  o Identify what kind of examples are lacking. You, the user, is needed
> >>    here. What do *you* think is missing, what would be helpful to show?
> >>
> >>  o Check what is needed to compile kernel-based examples over PPC 2.4.
> >>    Philippe indicated that some switches are likely missing (x86 is fine
> >>    already, other archs are 2.6-only).
> > 
> > Some time ago I sent a patch for RTnet using the "kernel CFLAGS
> > capturing" trick to get proper switches for 2.4:
> > 
> > http://sourceforge.net/mailarchive/forum.php?thread_id=9493711&forum_id=24610
> > 
> > 
> > We could do the same trick here.
> 
> Yeah, I had a look at this before. The point is that I would prefer to
> keep things _simple_ and self-contained. This capturing requires some
> helper Makefile and complex call nestings that likely only people with
> advanced make and shell skills can understand and adopt to their projects.

I tend to agree on the "keep it simple" mantra, but still, there are at
least two other aspects which are quite important too:

- Nobody should expect to be able to develop a complete project only
relying on paste-and-copy of example code. Since we are specifically
talking about Makefile rules, we could not provide any set that would
match everyone's project anyway, with respect to software and hardware
requirements. Therefore, at some point, people really need to know what
they are doing, which means that they should also know how to properly
build out-of-tree modules with _their_ own 2.4 setup (well, if any
"proper" solution exists, that is). And basically, I do hope that nobody
starts implementing kernel modules without having - at least - a vague
idea, about how to compile them for its platform in the first place...

- Given that there is life beyond x86, we need to make sure that all
Xenomai ports are considered equal, at least with respect to generic
issues. Whilst it's ok to provide a x86-only 2.4 Makefile for compiling
a x86-centric example, it's not for anything which could demonstrate a
feature on any platform.

This said, I agree that adding a fake module directory to capture the
flags set by the main kernel Makefile is one step beyond ugliness; the
other approach being to only provide a 2.6 Makefile frag. As 2007
approaches, I think that anyone still involved with projects relying on
2.4 kernels do know how to build 2.4 modules for the targeted platform.

> 
> But maybe things are that complicated already, and this is just
> different complexity. How do you compile simple out-of-tree modules
> against 2.4 PPC kernels? Are there any standard flags? Or is it
> different for each board or each compiler version or whatever?
> 
> Jan
> 
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-- 
Philippe.