From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2D5FACCF9E0 for ; Tue, 28 Oct 2025 10:16:36 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 8D17210E1A7; Tue, 28 Oct 2025 10:16:35 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=bootlin.com header.i=@bootlin.com header.b="y+8Q+f4+"; dkim-atps=neutral Received: from smtpout-04.galae.net (smtpout-04.galae.net [185.171.202.116]) by gabe.freedesktop.org (Postfix) with ESMTPS id BF7B210E1A7 for ; Tue, 28 Oct 2025 10:16:33 +0000 (UTC) Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-04.galae.net (Postfix) with ESMTPS id 9696AC0BE99; Tue, 28 Oct 2025 10:16:11 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id D17CA606AB; Tue, 28 Oct 2025 10:16:31 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 2136F1179B0FD; Tue, 28 Oct 2025 11:16:16 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1761646590; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding; bh=2y1VguXNadgmHV2MWfLxtHciagEfpDNKLtcTFrx9gQY=; b=y+8Q+f4+NyMBaI+oxtSqrmK40IPdzftk2i35ILp1mrzE1MtTvNNT2ZCztpZi7zowEFLzuk oiEQhsdjmNbXD2SyY4akCxVrmPgrlisRUbdzYuGNl97B+waeLpyRVBstpvylD0CaNWxrg8 5SOTPVtt7O7TNgXIFtY740KDEHoTgf4iKGRrceD8UhH66nWnP8FZKeCiz0e8qMpoQNxqT4 WBXUsn35LTLje4cB/nrYhZVTbCBmfRD8coW4iQaCvHD4J2paHoBeJUmwgf6YDMsGx/YCBn iijusX4eL6AszOvIZm3zo6vbow3B63MTv+llABtVDGO/yDMPHLAhibtPYziceA== From: Luca Ceresoli Subject: [PATCH v3 0/6] drm/bridge: enforce drm_bridge_add() before drm_bridge_attach() Date: Tue, 28 Oct 2025 11:15:41 +0100 Message-Id: <20251028-b4-drm-bridge-alloc-add-before-attach-v3-0-bb8611acbbfb@bootlin.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit X-B4-Tracking: v=1; b=H4sIAM2XAGkC/5WNwQ7CIBAFf8Vwdg1sa6ie/A/jARawJG0xQIim6 b9Le9KbHue9ZGZmyUZvEzvvZhZt8cmHqUKz3zHq1XS34E1lhhyPgvMGdAsmjqCjN/VUwxAIlDG grQuxDjkr6sG6RiBx3amOWHU9onX+uXWut8q9TznE15YtYl3/LRQBHE7odMsNSsnbiw4hD346U BjZ2ij44UXxqxerl4QkElo7J/HbuyzLG55mbsY0AQAA X-Change-ID: 20251003-b4-drm-bridge-alloc-add-before-attach-ef312c0b8a8c To: Alain Volmat , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Raphael Gallais-Pou , Andy Yan Cc: Hui Pu , Thomas Petazzoni , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Luca Ceresoli X-Mailer: b4 0.14.2 X-Last-TLS-Session-Version: TLSv1.3 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" This small series enforces that DRM bridges must be added before they are attached as discussed in [1]. This is part of the work towards removal of bridges from a still existing DRM pipeline without use-after-free. 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() [0]) 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 8. drm_of_find_panel_or_bridge, *_of_get_bridge 9. ➜ enforce drm_bridge_add before drm_bridge_attach 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 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) Series layout: - patches 1-2: add missing drm_bridge_add() to the 2 drivers known for not calling it - patch 3: document that drm_bridge_add() is required before attach - patch 4: add a warning in drm_bridge_attach() is drm_bridge_add() was not called - patch 5: add a warning for bridges missing both devm_drm_bridge_alloc() and drm_bridge_add() The added warning might reveal more non-compliant drivers, in that case they will be fixed as they are found. [0] https://lore.kernel.org/lkml/20250206-hotplug-drm-bridge-v6-0-9d6f2c9c3058@bootlin.com/#t [1] https://lore.kernel.org/all/20250709-sophisticated-loon-of-rain-6ccdd8@houat/ Signed-off-by: Luca Ceresoli --- Changes in v3: - Searched for any remaining drivers not calling drm_bridge_add(); found 1, added patch 6 to convert it - Added Suggested-by which was missing in patch 4, removed misplaced Link: tags - Added review tags to patches 1-2 - Link to v2: https://lore.kernel.org/r/20251021-b4-drm-bridge-alloc-add-before-attach-v2-0-c17cc1bbff72@bootlin.com Changes in v2: - Added patch 5 - Added review tags to patches 1-4 (patches unchanged) - Link to v1: https://lore.kernel.org/r/20251003-b4-drm-bridge-alloc-add-before-attach-v1-0-92fb40d27704@bootlin.com --- Luca Ceresoli (6): drm/sti: hda: add bridge before attaching drm/sti: hdmi: add bridge before attaching drm/bridge: document that adding a bridge is mandatory before attach drm/bridge: add warning for bridges attached without being added drm/bridge: add warning for bridges using neither devm_drm_bridge_alloc() nor drm_bridge_add() drm/bridge: synopsys: dw-dp: add bridge before attaching drivers/gpu/drm/bridge/synopsys/dw-dp.c | 2 ++ drivers/gpu/drm/drm_bridge.c | 9 +++++++++ drivers/gpu/drm/sti/sti_hda.c | 5 +++++ drivers/gpu/drm/sti/sti_hdmi.c | 2 ++ 4 files changed, 18 insertions(+) --- base-commit: 761105adbbac91d00a9662e54de1c55513556a48 change-id: 20251003-b4-drm-bridge-alloc-add-before-attach-ef312c0b8a8c Best regards, -- Luca Ceresoli