[bitbake-devel] User Manual: HelloWorld example questions.

[Bill Traynor]

On Wed, Jun 19, 2013 at 9:51 AM, Bill Traynor <btraynor at gmail.com> wrote:
> NOTE:  The following questions are posed within the context of the
> BitBake User Manual rewrite.
>
> In working through the following two HelloWorld examples:
>
> http://www.mail-archive.com/yocto@yoctoproject.org/msg09379.html
> http://hambedded.org/blog/2012/11/24/from-bitbake-hello-world-to-an-image/
>
> there are some concepts that I don't quite understand.
>
> 1.  The simplest HelloWorld possible would only require a recipe and
> source, correct?  The concepts of Classes and Layers is beyond the
> basics, is it not?  Or is the simplest of HelloWorld examples without
> concepts such as Classes and Layers essentially pointless?
>

To answer myself as I work through my hello world project from first
priciples, i.e. beginning with an empty directory and solving errors
one by one I realize that the concept of Layers is necessary given
that the first configuration file BitBake looks for is bblayers.conf,
which is where I set BBPATH.

> 2.  Why isn't there a sample base.bbclass in the bitbake source tree?

Oops, I meant a sample bblayers.conf, NOT base.bbclass which does
indeed exist.  Does it not make sense to have a bblayers.conf
containing at minimum:

BBPATH := "${TOPDIR}"

Perhaps even comment out the latter with a short explanation of what
un-commenting out implies?

>
> 3.  I think it would be very beneficial to understanding BitBake to
> build out the HelloWorld example beyond the basics, incorporating and
> explaining each concept along the way.  My thinking is that given the
> true value of BitBake is in the building of complex systems, it would
> be beneficial to walk through the concepts as simply as possible to
> demonstrate the concepts that require leverage to accomplish this.
> This would both demonstrate how BitBake works whiile avoiding overuse
> of OE or YP project examples.  Is this idea reasonable, or beyond the
> scope of the User manual?

I'm finding it very valuable to step through a simple example using
the -DDD debug parameter to understand what's going on when I issue
the BitBake command.

>
> That's all for now.  I appreciate the feedback.
>
> Bill