commit 6ecac85e upstream.

This should help with some of the lifetime issues, and move us away
from load/unload.

[rez] Regarding the backport to v4.14.y, the only difference is due to
the fact that in v4.14.y the udl_usb_probe() function still uses
drm_dev_unref() instead of drm_dev_put().

Backport notes:

On Mon, Jul 15, 2019 at 09:13:08PM -0400, Sasha Levin wrote:
> Hm, we don't need ac3b35f1 here? Why not? I'd love to document that
> with the backport.

Nope, we don't need that patch in the v4.14 backport.

In v4.19.y we have two functions, drm_dev_put() and drm_dev_unref(), which are
aliases for one another (drm_dev_unref() just calls drm_dev_put()).
drm_dev_unref() is the older of the two, and was introduced back in v4.0.
drm_dev_put() was introduced in v4.15 with

9a96f550 drm: introduce drm_dev_{get/put} functions

and slowly callers were moved from the old name (_unref) to the new name
(_put).  The ...