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

Luca Ceresoli
2025-11-19T13:06:03Z

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>