While changing the formfactor for a new board to turn on the touchscreen setting I found that it didn't give the expected results, and digging further showed it was because the machconfig that ended up being used was the empty default, instead of the one in the layer as it should have been. The output of log.do_unpack indeed shows that the machconfig being used isn't the one in the layer, but rather in meta: NOTE: Unpacking /usr/local/src/yocto/utrace/meta/recipes-bsp/formfactor/files/machconfig to /usr/local/src/yocto/utrace/build/tmp/work/sugarbay-poky-linux/formfactor-0.0-r20/ poky/master: ed44d29b9004ee355860d0d469dfe191dfcef184 meta-intel/master: 01d1a545477cbc1b2a1da5b66edb52fd9e783206
The issue here is the way I did the formfactor bbappend in meta-yocto. If we change that to use FILESEXTRAPATHS method and then use FILESEXTRAPATHS_prepend := in all layers above it then it works. Will submit a few patches to sort this out.
Patches have been merged in meta-yocto (e1f6ebba3ab2fc8a469c1d96fc6d4c4b8f16845c) and meta-intel (76d1178ba1a43cf6457c89717134aeb9f1275fae).
http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=e1f6ebba3ab2fc8a469c1d96fc6d4c4b8f16845c