[PATCH 00/26] drm/bridge: add drm_of_find_bridge(), deprecate of_drm_find_bridge()

[Luca Ceresoli <luca.ceresoli@bootlin.com>]

This series deprecated of_drm_find_bridge(), adds a replacement which
handles bridge refcounting, and converts most of the direct users.

This is part of the work to support hotplug of DRM bridges. The grand plan
was discussed in [0].

Here's the work breakdown (➜ marks the current series):

 1. ➜ add refcounting to DRM bridges struct drm_bridge,
      based on devm_drm_bridge_alloc()
    A. ✔ add new alloc API and refcounting (v6.16)
    B. ✔ convert all bridge drivers to new API (v6.17)
    C. ✔ kunit tests (v6.17)
    D. ✔ add get/put to drm_bridge_add/remove() + attach/detach()
         and warn on old allocation pattern (v6.17)
    E. ➜ add get/put on drm_bridge accessors
       1. ✔ drm_bridge_chain_get_first_bridge(), add cleanup action (v6.18)
       2. ✔ drm_bridge_get_prev_bridge() (v6.18)
       3. ✔ drm_bridge_get_next_bridge() (v6.19)
       4. ✔ drm_for_each_bridge_in_chain() (v6.19)
       5. ✔ drm_bridge_connector_init (v6.19)
       6. … protect encoder bridge chain with a mutex
       7. ➜ of_drm_find_bridge()
          a. ➜ add drm_of_fund_bridge(), convert most direct users
	  b. convert other direct users
	  c. convert bridge-only drm_of_find_panel_or_bridge() users
       8. drm_of_find_panel_or_bridge, *_of_get_bridge
       9. ✔ enforce drm_bridge_add before drm_bridge_attach (v6.19)
    F. ✔ debugfs improvements
       1. ✔ add top-level 'bridges' file (v6.16)
       2. ✔ show refcount and list lingering bridges (v6.19)
 2. … handle gracefully atomic updates during bridge removal
    A. … Add drm_dev_enter/exit() to protect device resources
    B. … protect private_obj removal from list
 3. … DSI host-device driver interaction
 4. ✔ removing the need for the "always-disconnected" connector
 5. finish the hotplug bridge work, moving code to the core and potentially
    removing the hotplug-bridge itself (this needs to be clarified as
    points 1-3 are developed)

[0] https://lore.kernel.org/lkml/20250206-hotplug-drm-bridge-v6-0-9d6f2c9c3058@bootlin.com/#t

Almost all the functions returning a struct drm_bridge pointer have been
modified to drm_bridge_get() the returned bridge, and their users updated
to drm_bridge_put() it.

of_drm_find_bridge() could be modified easily in the same way, but it has a
lot of (direct + indirect) callers, and most notably
drm_of_find_panel_or_bridge() which is very hard to adapt without reowrking
the panel_bridge lifetime.

Moreover of_drm_find_bridge() shold be called drm_of_find_bridge() by the
DRM subsystem conventions.

This has been discussed in [1] and Maxime proposed an incremental approach:

> One way to solve it would be that, for example, of_drm_find_bridge is
> oddly named according to our convention and it would make more sense to
> be called drm_of_find_bridge().
>
> So maybe we can just create drm_of_find_bridge() that takes a reference,
> make of_drm_find_bridge() deprecated in favour of drm_of_find_bridge(),
> add a TODO, and call it a day. People will gradually switch to the new
> API over time.

That proposal is implemented by this series. Most of the direct callers are
also converted: they are all trivial conversions except for one, which is
handled by the last 3 patches.

[1] https://lore.kernel.org/dri-devel/20250319-stylish-lime-mongoose-0a18ad@houat/

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
Luca Ceresoli (26):
      drm/bridge: add drm_of_find_bridge()
      drm/bridge: deprecate of_drm_find_bridge()
      drm/todo: add entry about converting to drm_of_find_bridge()
      drm/bridge: make of_drm_find_bridge() a wrapper of drm_of_find_bridge()
      drm/arcpgu: convert to drm_of_find_bridge()
      drm/bridge: add devm_drm_of_find_bridge
      drm/bridge: ite-it66121: use devm_drm_of_find_bridge() to put the next bridge
      drm/bridge: imx8qxp-pixel-combiner: use devm_drm_of_find_bridge() to put the next bridge
      drm/bridge: simple-bridge: use devm_drm_of_find_bridge() to put the next bridge
      drm/bridge: tpd12s015: use devm_drm_of_find_bridge() to put the next bridge
      drm/bridge: thc63lvd1024: use devm_drm_of_find_bridge() to put the next bridge
      drm/bridge: imx8qxp-pxl2dpi: use devm_drm_of_find_bridge() to put the next and companion bridges
      drm/bridge: lt8912b: use devm_drm_of_find_bridge() to put the hdmi bridge
      drm/bridge: tfp410: use devm_drm_of_find_bridge() to put the next bridge
      drm/bridge: imx8qxp-ldb: use devm_drm_of_find_bridge() to put the companion bridge
      drm/rcar-du: lvds: use devm_drm_of_find_bridge() to put the next bridge
      drm/meson: encoder_*: use devm_drm_of_find_bridge() to put the next bridge
      drm/bridge: sii902x: use devm_drm_of_find_bridge() to put the next bridge
      drm/mediatek: use devm_drm_of_find_bridge() to put the next bridge
      drm/kmb: dsi: use devm_drm_of_find_bridge() to put the next bridge
      drm/imx/ipuv3: use devm_drm_of_find_bridge() to put the next bridge
      drm/exynos: hdmi: use devm_drm_of_find_bridge() to put the next bridge
      drm/bridge: dw-hdmi: use devm_drm_of_find_bridge() to put the next bridge
      drm/bridge: imx8qxp-pixel-link: simplify logic to find next bridge
      drm/bridge: imx8qxp-pixel-link: simplify freeing of the remote device_node
      drm/bridge: imx8qxp-pixel-link: convert to drm_of_find_bridge()

 Documentation/gpu/todo.rst                         | 16 ++++++
 drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c           |  2 +-
 .../gpu/drm/bridge/imx/imx8qxp-pixel-combiner.c    |  2 +-
 drivers/gpu/drm/bridge/imx/imx8qxp-pixel-link.c    | 37 ++++++------
 drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c       |  4 +-
 drivers/gpu/drm/bridge/ite-it66121.c               |  2 +-
 drivers/gpu/drm/bridge/lontium-lt8912b.c           |  2 +-
 drivers/gpu/drm/bridge/sii902x.c                   |  2 +-
 drivers/gpu/drm/bridge/simple-bridge.c             |  2 +-
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c          |  2 +-
 drivers/gpu/drm/bridge/thc63lvd1024.c              |  2 +-
 drivers/gpu/drm/bridge/ti-tfp410.c                 |  2 +-
 drivers/gpu/drm/bridge/ti-tpd12s015.c              |  2 +-
 drivers/gpu/drm/drm_bridge.c                       | 66 ++++++++++++++++++++--
 drivers/gpu/drm/exynos/exynos_hdmi.c               |  2 +-
 drivers/gpu/drm/imx/ipuv3/dw_hdmi-imx.c            |  2 +-
 drivers/gpu/drm/kmb/kmb_dsi.c                      |  2 +-
 drivers/gpu/drm/mediatek/mtk_hdmi.c                |  2 +-
 drivers/gpu/drm/meson/meson_encoder_cvbs.c         |  2 +-
 drivers/gpu/drm/meson/meson_encoder_dsi.c          |  2 +-
 drivers/gpu/drm/meson/meson_encoder_hdmi.c         |  2 +-
 drivers/gpu/drm/renesas/rcar-du/rcar_lvds.c        |  2 +-
 drivers/gpu/drm/tiny/arcpgu.c                      |  4 +-
 include/drm/drm_bridge.h                           | 10 ++++
 24 files changed, 125 insertions(+), 48 deletions(-)
---
base-commit: 92c49b3f4df8f9acfa95551ef38fc00c675319fd
change-id: 20251117-drm-bridge-alloc-getput-drm_of_find_bridge-74903367448d

Best regards,
-- 
Luca Ceresoli <luca.ceresoli@bootlin.com>