[Openembedded-architecture] who should set default tunes?

[Denys Dmytriyenko]

On Tue, May 02, 2017 at 09:53:34PM +0100, Phil Blundell wrote:
> 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".

This notion is not OE specific - there are examples of binary distributions 
(Debian, Fedora, SuSE, etc.) and source distributions (Gentoo, LFS, CRUX, etc)
https://en.wikipedia.org/wiki/Category:Source-based_Linux_distributions


> 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.
> 
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