The demo SD card I got with my i.mx7d board has kernel 4.1.15. Linux boots and then loads an Xsession capable of calibrating the touch screen, connecting to a wireless network, running x11vnc, some demos etc.
I built a 4.9.88_2.0.0 image with the yocto build system (Also tried the prebuilt images to make sure) and Xorg is pretty much stock/empty. It won't start without modifying xorg.conf because the Driver line specifying vivante fails to load any drivers. If I remove that and just use Driver "fbdev" I can get it to launch Xorg. From there I can launch a window manager and X programs. I found several of the demos, a window manager and other odds and ends.
Am I missing a layer somewhere that contains all the configuration details to launch everything in a nice way? There seem to be other common configuration files not included in the build.. example /etc/network/interfaces