[PATCH v4 00/11] drm/bridge: handle refcounting for bridge-only callers of drm_of_find_panel_or_bridge()

[Luca Ceresoli]

This series converts all the bridge-only callers of the deprecated
drm_of_find_panel_or_bridge() API to a new, simpler API that handles bridge
refcounting.

All patches acked/reviewed except patches 3, 4 and 10.

== Series description

 * Patch 1 (new in v2) makes drm_bridge_get/put() ignore ERR_PTR pointers,
   not only NULL pointers
 * Patch 2 introduces of_drm_get_bridge_by_endpoint() as a replacement for
   bridge-only calls to drm_of_find_panel_or_bridge(); the new function
   refcounts the bridge and is simpler
 * The following patches convert all bridge-only users to the new API
 * The last patch forbids new bridge-only calls to
   drm_of_find_panel_or_bridge()

== Grand plan

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 (v7.2)
       7. ➜ of_drm_find_bridge
          a. ✔ add of_drm_get_bridge() (v7.0),
               convert basic direct users (v7.0-v7.1)
          b. ✔ convert direct of_drm_get_bridge() users, part 2 (v7.0)
          c. ✔ convert direct of_drm_get_bridge() users, part 3 (v7.0)
          d. ✔ convert direct of_drm_get_bridge() users, part 4 (v7.1-v7.2)
          e. ➜ 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_bridge_enter/exit() to protect device resources (v7.0)
    B. … protect private_obj removal from list
    C. ✔ Add drm_bridge_clear_and_put() (v7.1)
 3. … DSI host-device driver interaction
 4. ✔ removing the need for the "always-disconnected" connector
 5. ✔ Migrate i.MX LCDIF driver to bridge-connector (v7.2)
 6. … DRM bridge hotplug
    A. … Bridge hotplug management in the DRM core
       1. ✔ bridge-connector: attach encoder to the connector (v7.2)
    B.   Device tree description

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

Signed-off-by: Luca Ceresoli <luca.ceresoli at bootlin.com>
---
Changes in v4:
- Fixed patches 3 and 10
- Minor fixes to patches 1 and 2
- Removed bouncing addresses yongqin.liu at linaro.org and
  xinliang.liu at linaro.org from Cc
- Link to v3: https://patch.msgid.link/20260428-drm-bridge-alloc-getput-panel_or_bridge-v3-0-a537b5567add@bootlin.com

Changes in v3:
- patch 3, 8, 10: fixed ERR_PTR deref in the -ENODEV case, and removed
  Dmitry's R-by from those patches as they are changed
- Added review trailers to the other patches
- Link to v2: https://patch.msgid.link/20260428-drm-bridge-alloc-getput-panel_or_bridge-v2-0-4300744a1c47@bootlin.com

Changes in v2:
- Added patch to ignore ERR_PTR values in drm_bridge_get/put()
- Changed API to return the bridge (or a ERR_PTR) in the return value,
  not as a double-pointer output parameter
- Adapted all patches to the new API, dropped Dmitry's review tags as the
  patches are all modified
- Removed bouncing addresses from Cc list
- Link to v1: https://patch.msgid.link/20260413-drm-bridge-alloc-getput-panel_or_bridge-v1-0-acd01cd79a1f@bootlin.com

---
Luca Ceresoli (11):
      drm/bridge: drm_bridge_get/put(): ignore ERR_PTR
      drm/bridge: add of_drm_get_bridge_by_endpoint()
      drm/msm/hdmi: switch to of_drm_get_bridge_by_endpoint()
      drm/hisilicon/kirin: switch to of_drm_get_bridge_by_endpoint()
      drm/bridge: chrontel-ch7033: switch to of_drm_get_bridge_by_endpoint()
      drm/bridge: lontium-lt9611uxc: switch to of_drm_get_bridge_by_endpoint()
      drm/bridge: lt9611: switch to of_drm_get_bridge_by_endpoint()
      drm/bridge: adv7511: switch to of_drm_get_bridge_by_endpoint()
      drm/bridge: lt8713sx: switch to of_drm_get_bridge_by_endpoint()
      drm: zynqmp_dp: switch to of_drm_get_bridge_by_endpoint()
      drm: of: forbid bridge-only calls to drm_of_find_panel_or_bridge()

 drivers/gpu/drm/bridge/adv7511/adv7511.h     |  1 -
 drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 15 +++++----
 drivers/gpu/drm/bridge/chrontel-ch7033.c     | 28 ++++++++--------
 drivers/gpu/drm/bridge/lontium-lt8713sx.c    | 10 +++---
 drivers/gpu/drm/bridge/lontium-lt9611.c      |  9 +++--
 drivers/gpu/drm/bridge/lontium-lt9611uxc.c   |  9 +++--
 drivers/gpu/drm/drm_bridge.c                 | 49 +++++++++++++++++++++++++---
 drivers/gpu/drm/drm_of.c                     | 26 +++++++--------
 drivers/gpu/drm/hisilicon/kirin/dw_drm_dsi.c |  9 +++--
 drivers/gpu/drm/msm/hdmi/hdmi.c              | 14 ++++++--
 drivers/gpu/drm/xlnx/zynqmp_dp.c             | 19 ++++++-----
 include/drm/drm_bridge.h                     |  7 ++++
 12 files changed, 128 insertions(+), 68 deletions(-)
---
base-commit: 5919a056c7426ba74d0199252c7304566dadf161
change-id: 20260410-drm-bridge-alloc-getput-panel_or_bridge-42501b38eaad

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