[oe] Why PREFERRED_VERSION setting of <distro>.conf overrules local.conf setting ?

[Chris Larson]

On Tue, Aug 10, 2010 at 1:50 PM, Koen Kooi <k.kooi at student.utwente.nl>wrote:

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> On 10-08-10 01:15, Graham Gower wrote:
> > On 10 August 2010 04:31, Frans Meulenbroeks <fransmeulenbroeks at gmail.com>
> wrote:
> >> 2010/8/9 Chris Larson <clarson at kergoth.com>:
> >>> On Mon, Aug 9, 2010 at 6:26 AM, Hauser, Wolfgang (external) <
> >>> Wolfgang.Hauser.external at eads.com> wrote:
> >>>
> >>>> Hello,
> >>>>
> >>>> I want to change some used versions of packages, so I added a
> >>>> PREFERRED_VERSION_<package>="xxx" for the packages I want to have a
> >>>> special(newer) version to be used.
> >>>>
> >>>> But e. g. for busybox the version defined in the used <distro>.conf is
> >>>> used instead of my setting in local.conf.
> >>>>
> >>>> Should local.conf not overrule <distro/machine>.conf ??
> >>>
> >>>
> >>> Conceptually, local should override everything, as it's the "most
> specific"
> >>> information available, but from a technical standpoint, we can't parse
> the
> >>> machine and distro configs until local.conf is parsed, as that's
> usually
> >>> where the MACHINE and DISTRO are set.  You can use a 'local' override
> to get
> >>> around it, or you can ask the distro/machine maintainer to use ?=
> >>> assignments (set only if unset).
> >>>
> >>> PREFERRED_VERSION_<package>_local = "xxx" is how you use the override.
> >>
> >> The real solution woud be to either temporary store the
> >> PREFERRED_VERSION and apply it later on.
> >> Alternately we could parse local.conf twice, the first time ignoring
> >> the PREFERRED lines, and the 2nd time only looking at these.
> >> Yet another solution could be to split local.conf into two pieces, one
> >> with settings like MACHINE and DISTRO, the other one with the
> >> overrides.
> >
> > Wouldn't it be far simpler to fix the distro conf file(s)? E.g. apply
> > something like this:
> > s/^PREFERRED_VERSION_\([a-z]*\) =/PREFERRED_VERSION_\1 ?=/
>
> What's the point of setting a preferred version at all if you make it a
> weak assignment?
> The distro nearly always knows better and if you want to use a different
> version, sending a patch to change that version for review isn't exactly
> rocket science.


How about having decent usability?  The user asking for something and not
getting it is completely unintuitive.  If the user doesn't know what they
want, they won't request a specific version.  If they do request it, they
should get it, anything else is an OE usability issue.
-- 
Christopher Larson
clarson at kergoth dot com
Founder - BitBake, OpenEmbedded, OpenZaurus
Maintainer - Tslib
Senior Software Engineer, Mentor Graphics