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

Luca Ceresoli
2026-05-04T10:45:41Z

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@bootlin.com>
---
Changes in v4:
- Fixed patches 3 and 10
- Minor fixes to patches 1 and 2
- Removed bouncing addresses yongqin.liu@linaro.org and
xinliang.liu@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@bootlin.com>