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

[Keith Busch]

On Tue, Dec 01, 2020 at 07:57:32PM +0100, Javier González wrote:
> On 01.12.2020 23:03, Minwoo Im wrote:
> > > +
> > > +	device_initialize(&ns->cdev_device);
> > > +	ns->cdev_device.devt = MKDEV(MAJOR(nvme_ns_base_chr_devt),
> > > +				     ns->head->instance);
> > > +	ns->cdev_device.class = nvme_ns_class;
> > > +	ns->cdev_device.parent = ctrl->device;
> > > +	ns->cdev_device.groups = nvme_ns_char_id_attr_groups;
> > > +	dev_set_drvdata(&ns->cdev_device, ns);
> > > +
> > > +	sprintf(cdisk_name, "nvme%dc%dn%d", ctrl->subsys->instance,
> > > +			ctrl->instance, ns->head->instance);
> > 
> > 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.