[oe] How to rebuild images with updated PREFERRED_PROVIDER_xxx in machine conf?

[Jiason Li]

Hi,

I'm trying to rebuild images with updated PREFERRED_PROVIDER_xxx in
machine conf,
and I don't want to clean the whole oe/overlay/tmp directory each time
I bitbake an image.

I've setup an overlay with my own machine conf.

My steps:
1. bitbake some-image, oe/openembedded/recipes/some-pkg.bb was bitbaked.
2. bitbake -c clean some-pkg
3. bitbake some-pkg, according to the log,
oe/overlay/recipes/some-pkg-mine/some-pkg-mine.bb was bitbaked
correctly.
4. update machine conf with PREFERRED_PROVIDER_some-pkg = "some-pkg-mine"
5. bitbake some-image, but some-pkg was still bitbaked and was in
some-image, not some-pkg-mine!
6. rm -rf oe/overlay/tmp
7. bitbake some-image, this time some-pkg-mine is in some-image, finally.

So,
how do I rebuild an image with updated PREFERRED_PROVIDER_xxx in machine conf,
while not having to clean the whole oe/overlay/tmp directory each time?

Any info are very appreciated. :)

Thank you!
jiason
20100323