[OE-core] [PATCH 1/2] bitbake.conf: DISTRO_FEATURES as overrides

[Richard Purdie]

On Thu, 2017-06-08 at 08:04 +0200, Patrick Ohly wrote:
> On Wed, 2017-06-07 at 16:11 +0000, Peter Kjellerstedt wrote:
> > 
> > Rather than requiring that the wanted DISTRO_FEATURES that should
> > be 
> > available as overrides are defined in DISTRO_FEATURES_OVERRIDES
> > (which 
> > should not be confused with the similarly named
> > DISTROFEATURESOVERRIDES 
> > variable that you also add...),
> I had thought about those names and in the end went ahead with the
> similar names because the customizable one made sense to me and the
> internal one is similar to the other entries in OVERRIDES.
> 
> > 
> >  why not add them all but with a prefix. 
> > I.e., similar to how package names are available as overrides
> > prefixed 
> > with "pn-", how about all distro features are made available as 
> > overrides with a "df-" prefix?
> That would be fine with me.
> 
> I just have a few concerns:
>       * How performance-sensitive is OVERRIDES? How can the impact of
>         both approaches be benchmarked? The idea behind the
> configurable
>         subset was to add only a few new overrides. We currently have
>         almost 70 individual entries in DISTRO_FEATURES.
>       * I've seen confusion about the pn- prefix. At least df- would
> be
>         named appropriately (in contrast to PN, which is historic),
> but
>         it's yet another convention that might not be immediately
>         obvious. The same is true for selecting a subset with the
> same
>         name as the feature, though.
>       * Can distro features contain characters that are invalid in an
>         override? _ and : would have to be avoided, for example by
>         mapping them to -.

My feelings are:

* We need to use a prefix. We've been burnt too many times in the past 
  when not using these. "df-" is fine, users will just have to deal 
  with it.

* We should filter the list of overrides to those which the distro 
  wants to nominate. I really don't want to encourage wider spread of 
  things than we need to, these need to be conscious decisions.

Cheers,

Richard