cramfs + devfs

Does anyone here use cramfs or devfs together ?

At the moment I have a simple compressed ext2 ramdisk image included in
the kernel, but obviously this gets decompressed whenever the kernel
gets booted. I'd like to get rid of this and just mount either cramfs or
squashfs and decompress on the fly.

The trouble seems to be that with a cramfs root filesystem, if I use
devfs I cannot create new device nodes under /dev because the underlying
FS is read-only. The alternative is to throw out devfs and create these
nodes when generating the filesystem image, but because you need to be
root on the Linux box to use mknod that is not an option.

Is there some way of using, eg, tmpfs mounted on /dev and then mounting
devfs over that ?