[Buildroot] BR2_EXTERNAL - Broken in 2015.08.01????

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Dear Stephen Beckwith,

On Thu, 5 Nov 2015 16:57:56 -0500, Stephen Beckwith wrote:

>    After some more poking around, I was successful in getting the desired
> build to work.  Here is what I found:
> 1)  Typing "make" @ the top level does not seem to build the BR2_EXTERNAL
> code.  Is there something missing here?  Or is this by design? (based upon
> the fact that this code is not a "normal auto-something package") ??

No, this is not by design. "make" should build all packages you have
enabled in your configuration. If some packages don't get built even if
they are enabled in the configuration, it's because you didn't comply
with the naming conventions.

Package "foo" *must*:

 * Be implemented in package/foo/foo.mk
 * Have its Config.in option named BR2_PACKAGE_FOO
 * Use FOO_ as the prefix for all variables in foo.mk

> Questions:
> 1)  Can I have "layered" Config.in files in the BR2_EXTERNAL tree?  Or does
> it all have to be done in one? (currently, it is layered)

I'm not sure what you mean by "layered", but you definitely don't have
to put everything in one Config.in file, it can source other Config.in
files, like in Buildroot itself.

Have you read the documentation at
http://buildroot.org/downloads/manual/manual.html#customize-dir-structure ?
Also, read
http://free-electrons.com/doc/training/buildroot/buildroot-slides.pdf
starting from slide 230.

> 2)  Do I need to have a <directory>.mk for sub-directories, if they do
> nothing?  If I specify the correct path to find the <pkg>.mk from
> external.mk, is that OK?

Yes, it is OK. In fact, we suggest that external.mk should contain
something like:

include $(sort $(wildcard $(BR2_EXTERNAL)/package/*/*.mk))

> 3)  is the <PKG>_VERSION in the <pkg>.mk used in any way other than the
> build folder directory?

Yes, it is generally used to define <pkg>_SOURCE, either explicitly (in
your .mk file) or implicitly (if not provided in your .mk file).

I.e:

FOO_VERSION = 0.3.2
FOO_SOURCE = foo-$(FOO_VERSION).tar.xz

Or, when you don't explicitly give a value for FOO_SOURCE, the package
infrastructure will automatically give it the value
'<pkg>-$(FOO_VERSION).tar.gz'.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com