[Openembedded-architecture] layer.conf and layerindex change proposal

[Mark Hatle]

I've been looking at the layer.conf and layer index and think some minor changes
to the layer.conf could allow the layer index to be more powerful.

(background)

The layer index consists of:

name
summary
description
URL (git url)
web URL
usage url (docs?)
mailing list url

layer dependency -> required layer

recipes
machines
branches

The layer.conf file currently has:

BBFILE_COLLECTIONS

LAYERVERSION_<collection>
LAYERDEPENDS_<collection>


Assuming the BBFILE_COLLECTIONS is used to specify a unique name for this layer...


(proposal)

Currently the LAYERVERSION and LAYERDEPENDS can be used to automatically
construct the dependency/required information.  (It's not actually used this
way, but could be.)

Currently a lot of layers are not using these fields, but I would like to see
them become mandatory.  At a minimum each layer.conf should include 'core', even
better if they specified the version of core they were compatible with...

I'm thinking LAYERSUMMARY, LAYERDESCRIPTION, LAYERHOMEPAGE could easily be added
(but optional) so that a layer maintainer could specify values, and the layer
index could use these for populating the index.

In addition, many of the layers I work with have a clear set of required layers
(LAYERDEPENDS), but also have 'recommended' layers...  So I'd love to see a
LAYERRECOMMENDS as well.

For this one, in bitbake, we could add the LAYERRECOMMENDS to the priority
sorting code -- but if the layer is not included it's not an error or warning.


So the work required would be:

1) Verify LAYERVERSION and LAYERDEPENDS are defined by a layer.conf
   - 'core' would have an empty LAYERDEPENDS

1.1) Update the layer index to use these, which would require remembering the
BBFILE_COLLECTIONS name for each layer indexed, so it can be used for resolving
deps.

2) Add support for LAYERRECOMMENDS, require a small change to bitbake

3) Add LAYERSUMMARY, LAYERDESCRIPTION and LAYERHOMEPAGE to the
documentation.conf, and update the layerindex to use their fields if present.


Comments?  I know there had been some talk on removing the 'BBFILE_COLLECTIONS',
but then I don't see any other unique name for a layer... I'm not against moving
this, but I do think a unique layer name is needed... then the rest of these
items remain.

Thanks!
--Mark