I'm back to this discussion,
The original requirement of my first RFC patchset is mainly for Android Smartphone use case:
1. We want light on LCD and draw a logo immediately after power key press(don't consider uboot or lk biotloader here).
2. We want the whole kernel boot fast to give user the Android Launch deaktop
3. The modem initialization/reset is slow
4. The Touchpad firmware upgrade is slow
5. We have many cpu cores(up to 8 in latest exynos 5430 and MT6595...)
6. We have few schedulable/parallellizable threads
7. We compiled all of the modules in the kernel(stupid? avoid modprobe...but lose parallelization in userspace)
So, I think about is that possible to async most of the probes, but still reserve the requred dependencies to let them still work as expected.