[yocto] undocumented MACHINE_FEATURES, and what makes something a MACHINE feature?

[Robert P. J. Day]

On Fri, 15 Nov 2013, Burton, Ross wrote:

> On 15 November 2013 10:49, Robert P. J. Day <rpjday at crashcourse.ca> wrote:
> >   as you can see, the only tests for 'wifi' involve either
> > DISTRO_FEATURES or COMBINED_FEATURES, *not* MACHINE_FEATURES
> > individually. under the circumstances, then, can 'wifi' be considered
> > a legitimate MACHINE feature if it's never being tested in that
> > context? (the same can be said for 'bluetooth', by the way.)
>
> COMBINED_FEATURES is a union of MACHINE_ and DISTRO_FEATURES, ...

  i understand that part, but i'm still not convinced by the rest of
your argument, so let me walk through an example if i might. (it could
be that i'm massively overthinking this, but i've never been scared
about making an idiot of myself in the past so ...)

> so it does make sense for them to be listed as MACHINE_FEATURES as
> otherwise they can't be combined...  No point building wifi in the
> distro if the machine doesn't support it, and the machine supporting
> wifi isn't a reason to enable it in the distro.

  i (sort of) see your point, so let me use bluetooth as an example.
the ref manual currently lists bluetooth as both a valid DISTRO
feature and MACHINE feature so, AIUI, those two settings mean two
different things:

* MACHINE_FEATURES including bluetooth means that that machine has
actual integrated bluetooth, while
* DISTRO_FEATURES including bluetooth specifies that you *wish* to
include bluetooth software support in that distro

  so far, so good. but if i scan the entire dora source tree, the only
tests i see for the bluetooth "feature" are either checking
DISTRO_FEATURES or COMBINED_FEATURES, *none* checking MACHINE_FEATURES
specifically, and this strikes me as odd. i'm puzzled by the idea of
something being a valid MACHINE feature if nothing ever checks for
that.

  it seems like that leaves open the possibility of someone selecting
a DISTRO_FEATURES of bluetooth for a machine that doesn't even have
it. is that possible? does it make sense? am i just missing something
fundamental here?

rday

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
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