[PATCH 00/12] drm/bridge: convert users of of_drm_find_bridge(), part 2

[PATCH 00/12] drm/bridge: convert users of of_drm_find_bridge(), part 2

[Luca Ceresoli]

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@bootlin.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@bootlin.com>

[PATCH 01/12] drm: of: drm_of_panel_bridge_remove(): fix device_node leak

[Luca Ceresoli]

drm_of_panel_bridge_remove() uses of_graph_get_remote_node() to get a
device_node but does not put the node reference.

Fixes: c70087e8f16f ("drm/drm_of: add drm_of_panel_bridge_remove function")
Cc: stable@vger.kernel.org # v4.15
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
 include/drm/drm_of.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
index 7f0256dae3f1..f3e55ea2174c 100644
--- a/include/drm/drm_of.h
+++ b/include/drm/drm_of.h
@@ -5,6 +5,7 @@
 #include <linux/err.h>
 #include <linux/of_graph.h>
 #if IS_ENABLED(CONFIG_OF) && IS_ENABLED(CONFIG_DRM_PANEL_BRIDGE)
+#include <linux/of.h>
 #include <drm/drm_bridge.h>
 #endif
 
@@ -173,6 +174,8 @@ static inline int drm_of_panel_bridge_remove(const struct device_node *np,
 	bridge = of_drm_find_bridge(remote);
 	drm_panel_bridge_remove(bridge);
 
+	of_node_put(remote);
+
 	return 0;
 #else
 	return -EINVAL;

-- 
2.52.0

Re: [PATCH 01/12] drm: of: drm_of_panel_bridge_remove(): fix device_node leak

[Maxime Ripard]

On Wed, 7 Jan 2026 14:12:52 +0100, Luca Ceresoli wrote:
> drm_of_panel_bridge_remove() uses of_graph_get_remote_node() to get a
> device_node but does not put the node reference.
> 
> Fixes: c70087e8f16f ("drm/drm_of: add drm_of_panel_bridge_remove function")
> Cc: stable@vger.kernel.org # v4.15
> 
> [ ... ]

Acked-by: Maxime Ripard <mripard@kernel.org>

Thanks!
Maxime

Re: [PATCH 00/12] drm/bridge: convert users of of_drm_find_bridge(), part 2

[Marek Szyprowski]

On 07.01.2026 14:12, Luca Ceresoli wrote:
> 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].

This patchset breaks Exynos DSI (Samsung-DSIM) driver operation on all 
my test boards. I will try to debug it and provide more information 
tomorrow though.


> 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@bootlin.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,

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland