[poky] Order of .conf processing?

[Chris Larson]

On Mon, Jul 18, 2011 at 7:05 AM, Gary Thomas <gary at mlbassoc.com> wrote:
> On 07/18/2011 07:59 AM, Chris Larson wrote:
>>
>> On Mon, Jul 18, 2011 at 6:51 AM, Gary Thomas<gary at mlbassoc.com>  wrote:
>>>
>>> What's the order of processing of the various .conf files?
>>>
>>> It seems to me that bitbake.conf must be first as it seems
>>> impossible to override settings in that file using a soft
>>> assignment.  In particular, local.conf often has soft settings
>>> but these dont' seem to change what's in bitbake.conf
>>
>> BitBake only parses one global configuration file, bitbake.conf. It's
>> bitbake.conf that includes/requires all the other configuration files.
>> You can see the order by reading those inclusions in bitbake.conf.
>> Historically, the intention was for the configuration file load order
>> to be relatively parallel to the overrides order -- two different
>> mechanisms for implementing what is essentially a layered architecture
>> for the metadata, allowing, generally, more specific information to
>> override more general information. The configuration file order
>> differs slightly from that, however, as it's not possible to load the
>> distro or machine config files after local.conf, as local.conf is
>> generally where DISTRO and MACHINE are defined.
>
> In that case, isn't using ?= assignments in bitbake.conf a bit misleading?

First, there is one place variables can come from before the
configuration files, and that's the process environment, for variables
which aren't filtered out. Second, it could use ?= sanely after the
configuration files are included, as well.
-- 
Christopher Larson
clarson at kergoth dot com
Founder - BitBake, OpenEmbedded, OpenZaurus
Maintainer - Tslib
Senior Software Engineer, Mentor Graphics