[PATCH 4/4] nvme: enable char device per namespace

[Christoph Hellwig]

On Wed, Dec 02, 2020 at 04:30:02AM +0900, Keith Busch wrote:
> > > In multi-path, private namespaces for a head are not in /dev, so I don't
> > > think this will hurt private namespaces (e.g., nvme0c0n1), But it looks
> > > like it will make a little bit confusions between chardev and hidden blkdev.
> > > 
> > > I don't against to update nvme-cli things also even naming conventions are
> > > going to become different than nvmeXcYnZ.
> > 
> > Agree. But as I understand it, Keith had a good argument to keep names
> > aligned with the hidden bdev. 
> 
> My suggested naming makes it as obvious as possible that the character
> device in /dev/ and the hidden block device in /sys/ are referring to
> the same thing. What is confusing about that?
> 
> > It is also true that in that comment he suggested nesting the char
> > device in /dev/nvme
> 
> Yeah, I'm okay with sub-directories for these special handles, but there
> are arguments against it too. I don't feel that strongly about it either
> way.

I'd prefer different naming for the char vs the block devices.  Yes,
this will require a little work in the userspace tools to support the
character device, but I think it is much cleaner.

Devices in subdirectories of /dev/ are very rare and keep causing problem
with userspace tooling for the few drivers that use them, so I don't
think they are a good idea.