[Openembedded-architecture] who should set default tunes?

[Mark Hatle]

On 5/2/17 4:01 PM, Denys Dmytriyenko wrote:
> 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

I think this is where my view comes from.

Even Fedora (Red Hat) I view as a source distribution with different
instantiated versions (ARM, IA32, etc..)

The SRPM is the source and the 'distro' config, in one.  The build system then
applies the 'tune' and builds the package, producing a feed.

The 'feed' is what the binary distribution is made of.

--Mark

> 
>> 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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