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Fri, 26 Jun 2026 12:03:49 +0000 (UTC) Received: from [192.168.1.153] (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C2A7518005B1; Fri, 26 Jun 2026 12:03:30 +0000 (UTC) From: Albert Esteve Subject: [PATCH 0/5] drm/panel: refcounting panel lookups and references Date: Fri, 26 Jun 2026 14:03:22 +0200 Message-Id: <20260626-drm_refcount_wiring-v1-0-cca1a7b3bdef@redhat.com> Precedence: bulk X-Mailing-List: linux-sunxi@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-B4-Tracking: v=1; b=H4sIAAAAAAAC/x2MWwqAIBAAryL7naCVSV0lIsK22o801l4Q3T3pc 2BmHojIhBEa8QDjSZGCT6AzAW4Z/IySxsSQq7xSRhdy5LVnnFw4/N5fxORnWaJBayzWqrSQyi0 JdP/XtnvfD+CBweFlAAAA X-Change-ID: 20260513-drm_refcount_wiring-4e5e757e9047 To: Neil Armstrong , Jessica Zhang , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Andrzej Hajda , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , Inki Dae , Jagan Teki , Marek Szyprowski , Laurentiu Palcu , Lucas Stach , Frank Li , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Paul Cercueil , Linus Walleij , Marek Vasut , Stefan Agner , Tomi Valkeinen , Laurent Pinchart , Kieran Bingham , Geert Uytterhoeven , Magnus Damm , Biju Das , Sandy Huang , =?utf-8?q?Heiko_St=C3=BCbner?= , Andy Yan , Yannick Fertre , Raphael Gallais-Pou , Philippe Cornu , Maxime Coquelin , Alexandre Torgue , Chen-Yu Tsai , Samuel Holland , Jyri Sarha , Jingoo Han , Seung-Woo Kim , Kyungmin Park , Krzysztof Kozlowski , Peter Griffin , Alim Akhtar , Alison Wang , Paul Kocialkowski , Alain Volmat , Raphael Gallais-Pou , Thierry Reding , Mikko Perttunen , Jonathan Hunter Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-stm32@st-md-mailman.stormreply.com, linux-sunxi@lists.linux.dev, linux-samsung-soc@vger.kernel.org, linux-tegra@vger.kernel.org, Albert Esteve X-Developer-Signature: v=1; a=ed25519-sha256; t=1782475410; l=4786; i=aesteve@redhat.com; s=20260303; h=from:subject:message-id; bh=3BTWjIQGw6v603+MK6ywCULt+2ytc2OqbIhP38SSlXQ=; b=vLL8Ben9S7G7GBfAV5/dY7850AeH1O/rgqMk5FTgeHqnK1BhJ7ibVh3+QUe2vagwJMCyn90Tw qkWv9Fv/F5lBvW13X7zWOmhYBwLKK2ZIdvy06sPHln5E/gzS8WLH1Bj X-Developer-Key: i=aesteve@redhat.com; a=ed25519; pk=YSFz6sOHd2L45+Fr8DIvHTi6lSIjhLZ5T+rkxspJt1s= X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: r95R1cmxb6HDhYKQWfSqLllOEPgEdDv6gkvd16oO6Ro_1782475432 X-Mimecast-Originator: redhat.com X-MORS-Enabled: yes X-MORS-DOMAIN: patchwork.local X-MORS-HOSTING: hosting172546 X-MORS-USER: hosting172546 X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= The drm_panel subsystem provides kref-based reference counting [1] (drm_panel_get/put) but almost nothing in the tree actually uses it. This results in a systemic use-after-free pattern throughout the codebase. This series aims to close all those issues. Patches 1-2: fix the infrastructure. drm_panel_add/remove now keep a counted reference for the list entry. drm_panel_bridge_add_typed() now holds a counted reference for the lifetime of the panel_bridge. Patch 3: change the semantics of of_drm_find_panel() and find_panel_by_fwnode(). They now acquire a reference before returning, under panel_lock. Callers are responsible for calling drm_panel_put() when they no longer need the pointer. Patches 4-5: update all in-tree callers of of_drm_find_panel() and drm_of_find_panel_or_bridge() to release the reference at the appropriate point. Two patterns are repeated in these fixes: - Bridge-wrapping: the panel is passed to devm_drm_panel_bridge_add() or equivalent, which acquires its own reference. The caller (including devm_drm_of_get_bridge() and drmm_of_get_bridge()) releases its lookup reference immediately after. - Store-and-use: the panel pointer is kept in a driver struct and used directly for the device lifetime. The reference is released in the remove/unbind path, or via devm_add_action_or_reset() where no explicit teardown function exists. In order to catch all places in the tree that required releasing the reference, the search was assisted by an AI model. Specifically, a Coccinelle script was designed to address the trivial changes (not included in the series). Although a few required manual fixes, with goto labels or bracket additions. Additionally, the model helped to discern implicit teardown paths that were addressed with devm_add_action_or_reset() calls. Thus, these commits have the Assisted-by label following the project guidelines. No functional change is intended for any driver. The reference counting only affects object lifetime; panel operations are unaffected. [1] https://lore.kernel.org/all/20250331-b4-panel-refcounting-v4-0-dad50c60c6c9@redhat.com/ Signed-off-by: Albert Esteve --- Albert Esteve (5): drm/panel: have drm_panel_add/remove manage a list reference drm/bridge/panel: hold a reference to the wrapped panel drm/panel: make *find_panel*() return a counted reference drm/bridge: release panel reference on all lookup exit paths drm: release panel reference after panel bridge creation drivers/gpu/drm/bridge/analogix/analogix-anx6345.c | 3 +++ drivers/gpu/drm/bridge/panel.c | 18 ++++++++++++---- drivers/gpu/drm/drm_panel.c | 24 +++++++++++++++++----- drivers/gpu/drm/exynos/exynos_dp.c | 10 +++++++++ drivers/gpu/drm/exynos/exynos_drm_dpi.c | 3 +++ drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c | 18 ++++++++++++++++ drivers/gpu/drm/imx/dcss/dcss-kms.c | 3 +++ drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 4 +++- drivers/gpu/drm/logicvc/logicvc_interface.c | 12 +++++++++++ drivers/gpu/drm/mcde/mcde_drv.c | 1 + drivers/gpu/drm/mcde/mcde_dsi.c | 1 + drivers/gpu/drm/mxsfb/mxsfb_drv.c | 1 + drivers/gpu/drm/omapdrm/dss/output.c | 1 + drivers/gpu/drm/pl111/pl111_drv.c | 1 + drivers/gpu/drm/renesas/rcar-du/rcar_du_encoder.c | 1 + drivers/gpu/drm/renesas/rcar-du/rcar_lvds.c | 1 + drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c | 1 + drivers/gpu/drm/rockchip/analogix_dp-rockchip.c | 11 ++++++++++ drivers/gpu/drm/rockchip/rockchip_lvds.c | 1 + drivers/gpu/drm/rockchip/rockchip_rgb.c | 1 + drivers/gpu/drm/sti/sti_dvo.c | 3 +++ drivers/gpu/drm/stm/ltdc.c | 1 + drivers/gpu/drm/stm/lvds.c | 3 +++ drivers/gpu/drm/sun4i/sun4i_lvds.c | 13 ++++++++++++ drivers/gpu/drm/sun4i/sun4i_rgb.c | 13 ++++++++++++ drivers/gpu/drm/sun4i/sun4i_tcon.c | 2 ++ drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 2 ++ drivers/gpu/drm/tegra/dsi.c | 1 + drivers/gpu/drm/tegra/output.c | 3 +++ drivers/gpu/drm/tidss/tidss_kms.c | 16 ++++++++++----- drivers/gpu/drm/tve200/tve200_drv.c | 1 + 31 files changed, 159 insertions(+), 15 deletions(-) --- base-commit: 502d801f0ab03e4f32f9a33d203154ce84887921 change-id: 20260513-drm_refcount_wiring-4e5e757e9047 Best regards,