[OE-core] why conditional assignment of DEPLOY_DIR_IMAGE in bitbake.conf?

[Christopher Larson]

On Tue, Jul 22, 2014 at 9:36 AM, Robert P. J. Day <rpjday at crashcourse.ca>
wrote:

>   quite possibly another silly question, but i'm perusing poky's
> version of bitbake.conf and i see this:
>
> DEPLOY_DIR ?= "${TMPDIR}/deploy"
> DEPLOY_DIR_TAR = "${DEPLOY_DIR}/tar"
> DEPLOY_DIR_IPK = "${DEPLOY_DIR}/ipk"
> DEPLOY_DIR_RPM = "${DEPLOY_DIR}/rpm"
> DEPLOY_DIR_DEB = "${DEPLOY_DIR}/deb"
> DEPLOY_DIR_IMAGE ?= "${DEPLOY_DIR}/images/${MACHINE}"
> DEPLOY_DIR_TOOLS = "${DEPLOY_DIR}/tools"
>
>   now, what is the value of using "?=" to set DEPLOY_DIR_IMAGE, rather
> than just "=". i know what "?=" represents, but i normally expect to
> see it in a context where someone might have set it earlier to some
> other value, but this is in bitbake.conf, before any of the "include"
> or "require" directives to pull in any of the other .conf files. so in
> the midst of all those other DEPLOY_DIR_* hard assignments, why is the
> images directory a conditional install?
>

s/install/define/

If there's a ?= done before any includes in bitbake.conf, either its
position in the file has changed, or it's set that way to allow the user to
add those variables to the env whitelist and set them in the environment,
as the env is set before bitbake.conf is parsed.
-- 
Christopher Larson
clarson at kergoth dot com
Founder - BitBake, OpenEmbedded, OpenZaurus
Maintainer - Tslib
Senior Software Engineer, Mentor Graphics
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