Is there a way to get Linux to treat an initramfs as the final root filesystem?

I want to boot a system with an initramfs that's the actual final filesystem, not a temporary initramfs for loading drivers. Unfortunately, Linux imposes different (and in my case, undesirable) behaviors when using initramfs, including at least the following differences: - devtmpfs is not auto-mounted, at least not at first, but seems to get auto-mounted at some point later which I can't figure out. - Instead of running /sbin/init (or the init program specified by init= on the command line) the kernel attempts to invoke /init. I know it's possible to work around these by putting some extra junk on the initramfs, but I'd rather it just behave like a normal root fs. Is there any way to achieve this? If I do need to work around it with userspace scripting in the initramfs, I at least want to understand what triggers the auto-mounting of devtmpfs.