Message-Id: <20260107-drm-bridge-alloc-getput-drm_of_find_bridge-2-v1-0-283d7bba061a@bootlin.com>
Date: Wed, 07 Jan 2026 14:12:51 +0100
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Philippe Cornu <philippe.cornu@...com>, benjamin.gaignard@...aro.org, 
 Andrzej Hajda <andrzej.hajda@...el.com>, 
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
 Adrien Grassein <adrien.grassein@...il.com>, Liu Ying <victor.liu@....com>, 
 Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>, Inki Dae <inki.dae@...sung.com>, 
 Jagan Teki <jagan@...rulasolutions.com>, 
 Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Hui Pu <Hui.Pu@...ealthcare.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
 Luca Ceresoli <luca.ceresoli@...tlin.com>, stable@...r.kernel.org
Subject: [PATCH 00/12] drm/bridge: convert users of of_drm_find_bridge(),
 part 2

This series converts all DRM bridge drivers (*) from the now deprecated
of_drm_find_bridge() to its replacement of_drm_find_and_get_bridge() which
allows correct bridge refcounting. It also converts per-driver
"next_bridge" pointers to the unified drm_bridge::next_bridge which puts
the reference automatically on bridge deallocation.

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 of_drm_get_bridge(), convert basic direct users
	        (v6.20?, one driver still pending)
	  b. ➜ convert direct of_drm_get_bridge() users, part 2
	  c.   convert direct of_drm_get_bridge() users, part 3
	  d.   convert direct of_drm_get_bridge() users, part 4
	  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_dev_enter/exit() to protect device resources (v6.20?)
    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

This work is a continuation of the work to correctly handle bridge
refcounting for existing of_drm_find_bridge(). The ground work is in:

  - commit 293a8fd7721a ("drm/bridge: add of_drm_find_and_get_bridge()")
  - commit 9da0e06abda8 ("drm/bridge: deprecate of_drm_find_bridge()")
  - commit 3fdeae134ba9 ("drm/bridge: add next_bridge pointer to struct drm_bridge")

The whole conversion is split in multiple series to make the review process
a bit smoother. Parts 3 and 4 are converting non-bridge drivers (mostly
encoders).

(*) One bridge driver (synopsys/dw-hdmi) is converted in another series,
    together with its (non-bridge) users. Additionally this series converts
    drm_of_panel_bridge_remove() which is a special case, and has a bugfix
    for it too.

Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
---
Luca Ceresoli (12):
      drm: of: drm_of_panel_bridge_remove(): fix device_node leak
      drm: of: drm_of_panel_bridge_remove(): convert to of_drm_find_and_get_bridge()
      drm/bridge: sii902x: convert to of_drm_find_and_get_bridge()
      drm/bridge: thc63lvd1024: convert to of_drm_find_and_get_bridge()
      drm/bridge: tfp410: convert to of_drm_find_and_get_bridge()
      drm/bridge: tpd12s015: convert to of_drm_find_and_get_bridge()
      drm/bridge: lt8912b: convert to of_drm_find_and_get_bridge()
      drm/bridge: imx8mp-hdmi-pvi: convert to of_drm_find_and_get_bridge()
      drm/bridge: imx8qxp-ldb: convert to of_drm_find_and_get_bridge()
      drm/bridge: samsung-dsim: samsung_dsim_host_attach: use a temporary variable for the next bridge
      drm/bridge: samsung-dsim: samsung_dsim_host_attach: don't use the bridge pointer as an error indicator
      drm/bridge: samsung-dsim: samsung_dsim_host_attach: convert to of_drm_find_and_get_bridge()

 drivers/gpu/drm/bridge/imx/imx8mp-hdmi-pvi.c | 15 +++++++-------
 drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c     |  3 ++-
 drivers/gpu/drm/bridge/lontium-lt8912b.c     | 31 ++++++++++++++--------------
 drivers/gpu/drm/bridge/samsung-dsim.c        | 28 ++++++++++++++++---------
 drivers/gpu/drm/bridge/sii902x.c             |  7 +++----
 drivers/gpu/drm/bridge/thc63lvd1024.c        |  7 +++----
 drivers/gpu/drm/bridge/ti-tfp410.c           | 27 ++++++++++++------------
 drivers/gpu/drm/bridge/ti-tpd12s015.c        |  8 +++----
 include/drm/bridge/samsung-dsim.h            |  1 -
 include/drm/drm_of.h                         |  6 +++++-
 10 files changed, 69 insertions(+), 64 deletions(-)
---
base-commit: 2bcba510a612cea32b8a536eedeabd7fcb413cd0
change-id: 20251223-drm-bridge-alloc-getput-drm_of_find_bridge-2-12c6bbcb6896

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

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