[yocto] creating global variables in a recipes

[Joshua Immanuel]

Hello William, Christopher,

Thanks for the detailed explanation.

On Wed, 2012-02-01 at 11:50 -0500, William Mills wrote:
> I am not sure I can give you a better option that local.conf but I can
> explain why what your doing does not work.
> 
> It may feel from your usage that the image recipe is the ancestor of
> all the recipes but this is really not true.  The settings in a image
> recipe effect the assembly of that image and not the packages that
> they depend on.  An image could be assembled from packages that were
> built long ago or inherited via shared state.
> 
> settings in local,conf on the other hand affect all recipes.  If you
> add something there it will be seen by all recipes.  Unfortunately
> this means that all recipes are dependent on the settings and
> everything will need to be rebuilt in case the new setting effects
> them.  I believe this also means you will not be able to used share
> state with someone with a different setting of (or unset)
> SOME_VARIABLE.  (Well you can but you will both be rebuild
> everything.)
> 
> Alternatives to the whole approach are to make alternative packages
> for the various cases (busybox-minimal vs busybox-full) or use an
> image task to create an asset in the file system that then makes a
> difference at run time. 

My use-case is that I am creating an /etc/fstab file via
base-files.bbappend recipe. In that fstab, I use uuid (generated via
uuidgen) to denote different partition filesystems. So, I have to use
this uuid in the extended image_types.bbclass file to set them to the
generated partition images appropriately (via tune2fs).

One more approach I can think of is to echo the uuid to some file in the
deploy images directory (while creating the fstab file) and read them
back in image_types class. But this process looks messy.

Regards
Joshua
-- 
Joshua Immanuel
HiPro IT Solutions Private Limited
http://hipro.co.in
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