drm/udl: move to embedding drm device inside udl device.

drm/udl: move to embedding drm device inside udl device.

commit 6ecac85eadb9d4065b9038fa3d3c66d49038e14b 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 ac3b35f11a06 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

9a96f55034e41 drm: introduce drm_dev_{get/put} functions

and slowly callers were moved from the old name (_unref) to the new name
(_put).  The patch you mentioned, ac3b35f11a06, is one such patch where we are
replacing a drm_dev_unref() call with a drm_dev_put() call.  This doesn't have
a functional change, but was necessary so that the third patch in the v4.19.y
series I sent would apply cleanly.

For the v4.14.y series, though, the drm_dev_put() function hasn't yet been
defined and everyone is still using drm_dev_unref().  So, we don't need a
backport of ac3b35f11a06, and I also had a small backport change in the last
patch of the v4.14.y series where I had to change a drm_dev_put() call with a
drm_dev_unref() call.

Just for posterity, the drm_dev_unref() calls were eventually all changed to
drm_dev_put() in v5.0, and drm_dev_unref() was removed entirely.  That
happened with the following two patches:

808bad32ea423 drm: replace "drm_dev_unref" function with "drm_dev_put"
ba1d345401476 drm: remove deprecated "drm_dev_unref" function

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190405031715.5959-4-airlied@gmail.com
Signed-off-by: Ross Zwisler <zwisler@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>