Re: [PATCH 1/3] cdev: Finish the cdev api with queued mode support

[Dan Williams]

On Thu, Jan 21, 2021 at 12:13 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, Jan 20, 2021 at 11:38:57AM -0800, Dan Williams wrote:
> > -void cdev_del(struct cdev *p)
> > +void cdev_del(struct cdev *cdev)
> >  {
> > -     cdev_unmap(p->dev, p->count);
> > -     kobject_put(&p->kobj);
> > +     cdev_unmap(cdev->dev, cdev->count);
> > +     kobject_put(&cdev->kobj);
>
> After Christoph's patch series, the kobject in struct cdev does nothing,
> so I will be removing it.  So I don't think this patch set is going to
> do what you want :(

The proposal in this series has nothing to do with kobject lifetime.
Please take another look at the file_operations shutdown coordination
problem and the fact that it's not just cdev that has a use case to
manage file_operations this way. I believe Christoph's only objection,
correct me if I'm wrong, is that this proposal invents a new third way
to do this relative to procfs and debugfs. Perhaps there's a way to
generalize this for all three, and I'm going to put some thought
there, but at this point I think I'm failing to describe the problem
clearly.