[OE-core] [yocto] [yocto-docs][PATCH] kernel-dev: document the change detection of kernel feature files

[Urs Fässler]

On Tue, 2018-10-02 at 10:44 -0400, bruce.ashfielda wrote:
> On 2018-10-01 8:42 AM, Urs F?ssler wrote:
> > Recommend to add recipe-space features to SRC_URI so that changes
> > to them
> > are detected automatically.
> > 
> > Signed-off-by: Urs F?ssler <urs.fassler at bbv.ch>
> > Signed-off-by: Pascal Bach <pascal.bach at siemens.com>
> > ---
> >   documentation/kernel-dev/kernel-dev-common.xml | 7 +++++--
> >   1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/documentation/kernel-dev/kernel-dev-common.xml
> > b/documentation/kernel-dev/kernel-dev-common.xml
> > index 83b02b1c1..6289ce8d4 100644
> > --- a/documentation/kernel-dev/kernel-dev-common.xml
> > +++ b/documentation/kernel-dev/kernel-dev-common.xml
> > @@ -2623,6 +2623,9 @@
> >               <filename>.scc</filename> file in the
> >               <filename>SRC_URI</filename> statement to reference
> > multiple kernel
> >               features.
> > +            Since BitBake only detects changes on files listed in
> > +            <filename>SRC_URI</filename>, it is best to add all
> 
> This is not necessarily true. It would be better stated that if you
> are modifying the .cfg files in the layer directly, you should list
> them on the SRC_URI to have the changes picked up by bitbake.
> 
> It is not a matter of "best", so it should be stated that way.

Thank you for the feedback. I am not sure if I don't understand the
problem or your answer correctly.

We faced the problem, that our CI server did not picked up the changes
made in the .cfg files. I investigated the problem and found that
BitBake only detects changes on files listed in SRC_URI. This is
supported in the chapter "Working with Advanced Metadata" that states:

"BitBake parses [the .scc files] and fetches any files referenced in
the .scc files by the include, patch, or kconf commands. Because of
this, it is necessary to bump the recipe PR value when changing the
content of files not explicitly listed in the SRC_URI."
https://www.yoctoproject.org/docs/latest/mega-manual/mega-manual.html#recipe-space-metadata

The behavior is imho not what you expect. But fixing this is quite a
big change since it involves changes in the interaction of BitBake
(change detection on files) with Yocto classes (recursive parsing of
scc files). Therefore I try to solve it with a better description.

You stated that it is only necessary to add the .cfg files when you
change the .cfg files in the layer directly. I don't see how you would
change the .cfg files otherwise or what use case you have in mind.

> > @+            <filename>.cfg</filename> to
> > <filename>SRC_URI</filename>.
> >           </para>
> >   
> >           <para>
> > @@ -2674,10 +2677,10 @@
> >                       </para></listitem>
> >                   <listitem><para>
> >                       <emphasis>Add the Feature File to
> > <filename>SRC_URI</filename>:</emphasis>
> > -                    Add the <filename>.scc</filename> file to the
> > +                    Add the <filename>.cfg</filename> and
> > <filename>.scc</filename> file to the
> >                       recipe's <filename>SRC_URI</filename>
> > statement:
> >                       <literallayout class='monospaced'>
> > -     SRC_URI_append = " file://test.scc"
> > +     SRC_URI_append = " file://test.cfg file://test.scc"
> 
> This is wrong. You should not have both on the SRC_URI

I concluded this also from the description in the "Working with
Advanced Metadata" chapter (see above). But I would be happy to know
about another solution for our problem.

Urs

> >                       </literallayout>
> >                       The leading space before the path is
> > important as the
> >                       path is appended to the existing path.