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Message-ID: <77c70d7b-23bc-4f74-9a13-d10f4af132dd@samsung.com>
Date: Thu, 8 Jan 2026 00:48:24 +0100
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: Luca Ceresoli <luca.ceresoli@...tlin.com>, 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>
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, stable@...r.kernel.org
Subject: Re: [PATCH 00/12] drm/bridge: convert users of
of_drm_find_bridge(), part 2
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@...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,
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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