RFC Support template files for wic wks

From: Christopher Larson <[email protected]>

This adds support for .wks.in files as WKS_FILE.

These files are treated as the contents of a bitbake variable, so usual bitbake variable references are supported. I considered using another templating mechanism, for example the one used by yocto-layer, but then we'd end up largely mapping metadata variables to template fields anyway, which is a pointless indirection. Let bitbake expand the variables directly instead.

This feature lets us, for example, reference ${APPEND} in --append, and avoid hardcoding the serial console tty in the wks file, and let the user's changes to APPEND affect wic the way they do the other image construction mechanisms.

The template is read in and set in a variable at parse time, so changes to the variables referenced by the template will result in rebuilding the image.

It's been suggested that the name should better reflect how its contents are used, i.e. .bbin or so. I've also considered including something like 'bbv' or similar, to indicate its contents are that of a bitbake value. I think this should be discussed.

I'd love to hear questions or comments on this. I think the value is clear, and it's something we need to solve, but I'd like to hear if others agree or disagree on that, and whether this implementation is appropriate.

The following changes since commit 1a0e56630c5c27d8899dd0979ae0b86bbe227881:

utils.bbclass: note for deprecated base_contains (2016-04-29 07:53:58 +0100)

are available in the git repository at:

git://github.com/kergoth/openembedded-core wks.in
https://github.com/kergoth/openembedded-core/tree/wks.in

Christopher Larson (3):
image.bbclass: append to prefuncs/postfuncs for do_image_* image_types.bbclass: add intermediate var for WKS_FILE_CHECKSUM image_types.bbclass: support template .wks.in files for wic

 meta/classes/image.bbclass       |  4 ++--
 meta/classes/image_types.bbclass | 38 +++++++++++++++++++++++++++++++++++++-
 2 files changed, 39 insertions(+), 3 deletions(-)

2.8.0