futher decouple DAX from block devices

[Christoph Hellwig]

On Thu, Nov 04, 2021 at 10:34:17AM -0700, Darrick J. Wong wrote:
> /me wonders, are block devices going away?  Will mkfs.xfs have to learn
> how to talk to certain chardevs?  I guess jffs2 and others already do
> that kind of thing... but I suppose I can wait for the real draft to
> show up to ramble further. ;)

Right now I've mostly been looking into the kernel side.  An no, I
do not expect /dev/pmem* to go away as you'll still need it for a
not DAX aware file system and/or application (such as mkfs initially).

But yes, just pointing mkfs to the chardev should be doable with very
little work.  We can point it to a regular file after all.