Formatting of backing device

Hi all,

first of all I would like to congratulate for this
project, I think it is one of the most promising
feature the Linux kernel can have.

Wrote that, I've a question about the concept of
formatting the backing device.

As far as I understood, the first concept of bcache
was to simply "register" or "attach" a cache to a
backing device, that is, the backing device had not
to be formatted.

Lately, still if I understood it correctly, this
behaviour was changed and, now, the backing device
needs to be formatted.

So, the question is:

How about an already running device? Is it still
possible to attach a cache under such situation?

In general, would it be possible to attach/detach
a cache to any already available device (in the
future)? Or the caching/backing setup must be planned
before the HW is available, so to speak?

It would be useful (and cool too), to have the
possibility to attach/detach the SSD cache, on
the fly (at run-time) to any device it needs it.

I hope the question(s) are clear, if not please
let me know.

Thanks a lot in advance,

bye,

-- 

piergiorgio