On Mon, May 25, 2020 at 03:10:39PM +0200, Martin Jansa wrote:

You can add a layer which will set LAYERSERIES_COMPAT for another layer,
but it needs to be parsed before the layer you want to change, e.g.:
https://github.com/webosose/meta-webosose/blob/thud/meta-qt5-compat/conf/layer.conf
it's useful to use this layer also to implement whatever modifications are
needed to make the layer to be actually compatible with the release you're
using, like:
https://github.com/webOS-ports/meta-webos-ports/tree/zeus/meta-qt5-compat

FWIW, you could make the parsing order not matter (at least in thud,
from a quick look, master as well). LAYERSERIES_COMPAT is resolved after
all layer.conf have been parsed[1]. I do not know if it's on purpose or
not, meaning it could well disappear in the near future.

So you could override it from anywhere by using __append but it has to
be done before or during the conf/layer.conf parsing. This also makes it
future proof wrt layer priorities and how LAYERSERIES_COMPAT is set (+=,
=, ?= ?).

I personally have it in conf/bblayers.conf (for some reason we "ship"
this one, though it's not best practice IIRC).

[1] https://git.yoctoproject.org/cgit.cgi/poky/tree/bitbake/lib/bb/cookerdata.py?h=thud#n399

Cheers,
Quentin