[Buildroot] Using udev, non-static /dev, and ramfs (or tmpfs)

[don]

I have a buildroot system that has been working fine (thanks) using
a static /dev in a ramfs rootfs.  Now I want to add a USB device and it 
seems like I should let udev etc. handle it.

However udev cannot make entries in a read-only /dev.

Is there a simple recipe for mounting /dev as writable?

There are several compilcations:

	Normally to mount with ramfs I'd use /dev/ram*.  
	How does that work with mounting /dev?

	What about all the existing static /dev/entries?

I see that /etc/init.d/S10udev tries to use "/sbin/udevstart", but
I don't have that.

Would I be better off to keep things static?

Thanks
Don Reid