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Message-Id: <20250314-drm-bridge-refcount-v7-0-152571f8c694@bootlin.com>
Date: Fri, 14 Mar 2025 11:31:13 +0100
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: 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>,
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>,
Marek Vasut <marex@...x.de>, Stefan Agner <stefan@...er.ch>,
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: Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
Anusha Srivatsa <asrivats@...hat.com>,
Paul Kocialkowski <paulk@...-base.io>, Dmitry Baryshkov <lumag@...nel.org>,
Hervé Codina <herve.codina@...tlin.com>,
Hui Pu <Hui.Pu@...ealthcare.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>
Subject: [PATCH v7 00/11] drm/bridge: add devm_drm_bridge_alloc() with
bridge refcount
This series improves the way DRM bridges are allocated and initialized and
makes them reference-counted. The goal of reference counting is to avoid
use-after-free by drivers which got a pointer to a bridge and keep it
stored and used even after the bridge has been deallocated.
The overall goal is supporting Linux devices with a DRM pipeline whose
final components can be hot-plugged and hot-unplugged, including one or
more bridges. For more details see the big picture [0].
DRM bridge drivers will have to be adapted to the new API, which is pretty
simple for most cases. Refcounting will have to be adopted on the two
sides: all functions returning a bridge pointer and all code obtaining such
a pointer. This series has just an overview of some of those conversions,
because for now the main goal is to agree on the API.
Series layout:
1. Add the new API and refcounting:
drm/bridge: add devm_drm_bridge_alloc()
drm/bridge: add support for refcounting
2. get/put the reference in basic operations in the bridge core:
drm/bridge: get/put the bridge reference in drm_bridge_add/remove()
drm/bridge: get/put the bridge reference in drm_bridge_attach/detach()
3. as an example of changes for bridge consumers, get a reference for the
bridge returned by drm_bridge_chain_get_first_bridge(), have it put by
all callers (all users will be covered later on separately):
drm/bridge: add a cleanup action for scope-based drm_bridge_put() invocation
drm/bridge: get the bridge returned by drm_bridge_chain_get_first_bridge()
drm/mxsfb: put the bridge returned by drm_bridge_chain_get_first_bridge()
drm/atomic-helper: put the bridge returned by drm_bridge_chain_get_first_bridge()
drm/probe-helper: put the bridge returned by drm_bridge_chain_get_first_bridge()
4. convert a few bridge drivers (bridge providers) to the new API:
drm/bridge: ti-sn65dsi83: use dynamic lifetime management
drm/bridge: samsung-dsim: use dynamic lifetime management
This work was formerly a part of my v6 DRM bridge hotplug series[0], now
split as a standalone series with many improvements, hence the "v7" version
number.
[0] https://lore.kernel.org/dri-devel/20250206-hotplug-drm-bridge-v6-0-9d6f2c9c3058@bootlin.com/
Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
---
Luca Ceresoli (11):
drm/bridge: add devm_drm_bridge_alloc()
drm/bridge: add support for refcounting
drm/bridge: get/put the bridge reference in drm_bridge_add/remove()
drm/bridge: get/put the bridge reference in drm_bridge_attach/detach()
drm/bridge: add a cleanup action for scope-based drm_bridge_put() invocation
drm/bridge: get the bridge returned by drm_bridge_chain_get_first_bridge()
drm/mxsfb: put the bridge returned by drm_bridge_chain_get_first_bridge()
drm/atomic-helper: put the bridge returned by drm_bridge_chain_get_first_bridge()
drm/probe-helper: put the bridge returned by drm_bridge_chain_get_first_bridge()
drm/bridge: ti-sn65dsi83: use dynamic lifetime management
drm/bridge: samsung-dsim: use dynamic lifetime management
drivers/gpu/drm/bridge/samsung-dsim.c | 7 +-
drivers/gpu/drm/bridge/ti-sn65dsi83.c | 7 +-
drivers/gpu/drm/drm_atomic_helper.c | 5 ++
drivers/gpu/drm/drm_bridge.c | 74 +++++++++++++++++++--
drivers/gpu/drm/drm_probe_helper.c | 1 +
drivers/gpu/drm/mxsfb/lcdif_kms.c | 3 +-
include/drm/drm_bridge.h | 119 +++++++++++++++++++++++++++++++++-
7 files changed, 201 insertions(+), 15 deletions(-)
---
base-commit: 9e6d91c60b0d64a4f945663993b3bbf4f3fb7392
change-id: 20250314-drm-bridge-refcount-58d9503503f6
Best regards,
--
Luca Ceresoli <luca.ceresoli@...tlin.com>
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