Linux kernel recipe override question

[John Weber <rjohnweber@gmail.com>]

Here is a question someone might be able to quickly answer.

I want to be able to override the SRCREV, SRCBRANCH, and the git repository for
the kernel recipe in local.conf.  I like to do this so that I can do local
hacking on a kernel without having to edit the recipe files themselves, and I
find that managing local.conf is easier when I'm changing SRCREVs a lot.

I've been able to override SRCBRANCH by doing this:

In recipes-kernel/linux/linux-wandboard.inc:

SRCBRANCH ??= "master"

The default is set in recipes-kernel/linux/linux-wandboard_3.10.17.bb:

SRCBRANCH ?= "<the-default-branch>"

Then, in local.conf, I can override it:

SRCBRANCH_linux-wandboard = "<my-local-hacking-branch>"

This works fine for SRCBRANCH. If I do the same thing with SRCREV, it doesn't
seem to work.  I've done this:

In linux-wandboard_3.10.17.bb:

SRCREV ??= "<default big long commit id>"

In local.conf:

SRCREV_linux-wandboard = "<my local branch commit id>"

I always get the checkout of the SRCREV assignment done in the recipe file, not
the one I set in local.conf.

Any idea why?  The only thing I can think of is that SRCREV is evaluated completely before
local.conf settings are evaluated.

John