On Wed, May 22, 2013 at 3:14 AM, Phil Blundell <p...@pbcl.net> wrote:
> On Wed, 2013-05-22 at 09:47 +0100, Paul Barker wrote: > > I've just sent a patch to the yocto@ list to fix this but it's brought > > up two things: > > > > 1) In openembedded-core/meta/classes/image.bbclass SPLASH is set with > > '?='. I'm overriding this with '=' in > > meta-raspberrypi/conf/machine/raspberrypi.conf which means it can't be > > overridden further in local.conf. Is this worth changing to '??=' in > > image.bbclass, '?=' in the machine conf so that it can be overridden > > with '=' in local.conf? Is my understanding of the overrides correct > > here? > > You can always override it from local.conf using a _forcevariable > override (which used to be named "_local", in fact, but that terminology > turned out to be a bit confusing), or a _MACHINE override of course. So > I don't think there is any major problem here. > > But, that said, it probably is true that the semantics of ??= are less > surprising for users (since it isn't position-dependent in the way > that ?= is) which might make it a better choice for image.bbclass. ??= is great in config files, but not ideal in classes that aren't globally inherited. If bitbake.conf sets a ??=, and a distro .conf updates the default by using ??= again, and then the class uses ??=, it'll replace the latest default set by the config. So, I think for default values, classes should use ?=, config files should use ??=. -- Christopher Larson clarson at kergoth dot com Founder - BitBake, OpenEmbedded, OpenZaurus Maintainer - Tslib Senior Software Engineer, Mentor Graphics
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