[Openembedded-architecture] who should set default tunes?

[Phil Blundell]

On Tue, 2017-05-02 at 15:29 -0500, Mark Hatle wrote:
> On 5/2/17 2:41 PM, Phil Blundell wrote:
> > 
- what upgrade and/or downgrade paths it wants to provide;
> > 
> > - what political considerations (e.g. around endianness) it might
> > have
> > to take into account;
> > 
> > - and no doubt many other things that might influence binary
> > compatibility in one way or another.
> 
> local project or BSP (via the tunes) is what I use to set these.  My
> distributions don't have these concerns.

If your distributions don't have those concerns then they are not
distributions, at least not in the sense that we've previously used
this terminology in OE.  I think a lot of what you consider to be
"local project" configuration is what would by previous OE conventions
be part of the DISTRO.  Indeed, central to the concept of a DISTRO is
that it completely defines the binary compatibility layer and,
consequently, admits no local tinkering that would have an impact on
the ABI of the binaries it generates.  It sounds as though the meaning
you are ascribing to DISTRO is more like "collection of source package
options" and less like "full set of policies that will result in a
coherent binary distribution".

If you take a pre-existing DISTRO and then make some sort of
configuration change to it via local.conf such that it is no longer
binary compatible, you have effectively forked it into your own
distribution.  That's not necessarily a bad thing, but it's no longer
the same DISTRO.

Now, of course, it would be perfectly legitimate for a DISTRO to say
that it doesn't care at all about binary compatibility between
MACHINES, that it wants to build everything with PACKAGE_ARCH = MACHINE
and that it wants every binary to be tuned to the limit.  In that
situation it might be useful for the BSP to expose some information
that the DISTRO could use to obtain these results, i.e. "these are the
settings that, if no other considerations apply, I would like you to
use".  But this should not diminish the primacy of the DISTRO when it
comes to making its own ABI choices.

p.