Re: [PATCH v6 02/16] chardev: introduce cdev_get_by_path()

Matthew Wilcox
2019-07-25T17:58:37Z

On Thu, Jul 25, 2019 at 11:53:20AM -0600, Logan Gunthorpe wrote:
>
>
> On 2019-07-25 11:40 a.m., Greg Kroah-Hartman wrote:
> > On Thu, Jul 25, 2019 at 11:23:21AM -0600, Logan Gunthorpe wrote:
> >> cdev_get_by_path() attempts to retrieve a struct cdev from
> >> a path name. It is analagous to blkdev_get_by_path().
> >>
> >> This will be necessary to create a nvme_ctrl_get_by_path()to
> >> support NVMe-OF passthru.
> >
> > Ick, why? Why would a cdev have a "pathname"?
>
> So we can go from "/dev/nvme0" (which points to a char device) to its
> struct cdev and eventually it's struct nvme_ctrl. Doing it this way also
> allows supporting symlinks that might be created by udev rules.

But you're not really trying to go from a string to a chardev. You're
trying to go from a nvmet_subsys to a chardev. Isn't there a better
way to link the two somewhere else?

(I must confess that once I would have known the answer to this, but
the NVMe subsystem has grown ridiculously complex and I can no longer
fit it in my head)