From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout-02.galae.net (smtpout-02.galae.net [185.246.84.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0FD813FBA7 for ; Tue, 21 Oct 2025 21:01:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.246.84.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761080484; cv=none; b=fdozphHbp0aNvpYtdhuEz+Iw/0l7jiu/FE7v3PnQ8hSXxfzXgyI3gf6j8w8Lt4WPiIBIy1gq3C9tY+PiRrTvIWAswXl4BrDO0JW6hBUwuYuUplZxClxGYAHDCkYzXCVal7LiYKK546f7ICe8BIhKIn6hMb4zgwPZ9uEFIFhNIUE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761080484; c=relaxed/simple; bh=EAI/Y6nsft/bHHXZ40zvJjSM8UEnKMb40D2gEvFGtK0=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=X1Vcskv3j89RREB+Gzkd/5my4DfcfpRlmmkHXmcmeXgTDERRgMoOvRGcNwGnkPxwdPAhKP6TGL+VofH//0zzNwEzzZd7yAtZddqptP9T4hc6S1xGmkF7aGjaNZueT3K7BLYlgZm0anPbupl4Tkb6PcPgnTwqXNrEBZc+681xaG0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=ewEDuw8L; arc=none smtp.client-ip=185.246.84.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="ewEDuw8L" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-02.galae.net (Postfix) with ESMTPS id 1C39E1A15AB; Tue, 21 Oct 2025 21:01:18 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id D890F60680; Tue, 21 Oct 2025 21:01:17 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id AA96A102F2415; Tue, 21 Oct 2025 23:00:56 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1761080476; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding; bh=StWZV3qPQUGaxlrgnNwyHxQJLDbPYSKXBfhgcG7aLzo=; b=ewEDuw8LXOPWt52sCLrhohoFRi4re2+XU0UoggViAiOe8SBIB/IGOo5ha4XHEIn2Jd7QPv X7XL8P/XsoxItFymzcyJ1/0vV57BjBZ5MCcXEGWO5M5jFtThXMa/uH0nsaWsRrH6rkngWu uUouW/Pna6352LY4mKxQaHSXCs5aIx0f2y0lfCI7129NAy7iKJVTT4Yer/0pXSxq9BsWaN QmRIpgN8MM4Cm6G4wxlv5Ra+EKqkIbkWWMMh5oWcOkmuIkiF0HoywjZjhH4J6/l6WYfFnm /3soE/fjlQP2A5KI/7/lgvoigd3s0jSPZ4sx1Sr6t5ZSzHW7C7hQTixY2DiFvA== From: Luca Ceresoli Subject: [PATCH v2 0/5] drm/bridge: enforce drm_bridge_add() before drm_bridge_attach() Date: Tue, 21 Oct 2025 23:00:43 +0200 Message-Id: <20251021-b4-drm-bridge-alloc-add-before-attach-v2-0-c17cc1bbff72@bootlin.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit X-B4-Tracking: v=1; b=H4sIAHv092gC/5WNTQ6CMBBGr0K6dkxbMKAr72FY9GcqkwA106bRE O5u5QYu3/uS720iIRMmcWs2wVgoUVwr6FMj3GTWJwL5ykJLfVFStmA78LyAZfJ1NPMcHRjvwWK IXEXOxk2AoVXaSTuYwYn69WIM9D46j7HyRClH/hzZon7230JRIOGqg+2k130vu7uNMc+0nl1cx Ljv+xe9icrx3AAAAA== X-Change-ID: 20251003-b4-drm-bridge-alloc-add-before-attach-ef312c0b8a8c To: Alain Volmat , Raphael Gallais-Pou , 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 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 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 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 (5): 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() drivers/gpu/drm/drm_bridge.c | 9 +++++++++ drivers/gpu/drm/sti/sti_hda.c | 5 +++++ drivers/gpu/drm/sti/sti_hdmi.c | 2 ++ 3 files changed, 16 insertions(+) --- base-commit: c1a7cc00cd412505e070eb4e62bc0b0ca85243e0 change-id: 20251003-b4-drm-bridge-alloc-add-before-attach-ef312c0b8a8c Best regards, -- Luca Ceresoli