From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout-04.galae.net (smtpout-04.galae.net [185.171.202.116]) (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 5628033F6 for ; Fri, 3 Oct 2025 09:00:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.171.202.116 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759482047; cv=none; b=mBkmCaarMETmXVsMLF2vB0vO3727D9ZRpctLvDWkFpUhX5g3l9nQ/0tgAbCUZ+NZS7g4Jrbt3yc7oWMvFhWtUQUJOZHGycEWSO+s+4ZFYzUwoy6po3VfCVb5HL0ZnjxcUV2n8EvDJ1PAu0bZRKkhGg5z/TDz35Yi3yLCDR9+cc4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759482047; c=relaxed/simple; bh=NbAaPYZrppMAs8ZuMrfKU+8LcY5bRMhyujbIEj5X4wI=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=bh8noGbK726Ol7zEN6+LKUT0sscsOm4lBmKwQNkuSzGlbrYk0sEs3IVZ+UcL74PBGGYRgLMophlDP/klIXzpqY7uMhQOiRhx3tfge0jIWotq7C/rPI9PzqM6kgiN375E0Zh4TUp+fFnJy0ElIierJrOSMFsGApNc+zCe/Nf/+s4= 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=YymIYJaE; arc=none smtp.client-ip=185.171.202.116 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="YymIYJaE" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-04.galae.net (Postfix) with ESMTPS id 629CFC00D93; Fri, 3 Oct 2025 09:00:24 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id 4F7BF60683; Fri, 3 Oct 2025 09:00:42 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id A57F7102F1C39; Fri, 3 Oct 2025 11:00:28 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1759482041; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding; bh=ydVaQXOs3El6RgjJFLU2RI0S1jr8ahmEJkfZ2n2xcVw=; b=YymIYJaE0nPg/qfX9fcdUI9vphYazKAB1w6MwQzABk9gmm9+zRKAFB/6ki2ohQ91P/XnCa uxkQclcOdFk2ojxQVeskT7HZsFXa8nLtWBXbRk7oQKYmJdfzKwiNYjkV3fRXo+xogE1Ty9 ZYEQHJLMrntPCm5i5O+bKp4Xvb7IW2MgwV1jKI9J+9QCQlbeT3JHkaYNxyOgi6KwRtSisc LaE5XVKIJkRIRGuIpLsCl64Hmd3Td4ZLwK1aA9ushm+ubyTXT5YNIKMdVDr306b6JSZUEj RIqUgPY2ucRrkgH21/vWb3wCxKk+CrSBvBwRBT1AhxjAAEzUHRSrvWbjDrIaEQ== From: Luca Ceresoli Subject: [PATCH 0/4] drm/bridge: enforce drm_bridge_add() before drm_bridge_attach() Date: Fri, 03 Oct 2025 10:59:54 +0200 Message-Id: <20251003-b4-drm-bridge-alloc-add-before-attach-v1-0-92fb40d27704@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=H4sIAIqQ32gC/x2N0QrCMAxFf2Xk2UDbKQx/RXxok9QF5irpGMLYv xt8PPfAPQd0MZUO9+EAk127ttUhXgagOa8vQWVnSCHdYggjliuyvbGYssu8LI0wM2OR2syHbcs 0o9QxJgplyhOBf31Mqn7/ncfzPH8kF4pndwAAAA== 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 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 a cleanup action (drm-misc-next) 2. ✔ drm_bridge_get_prev_bridge() (drm-misc-next) 3. ✔ drm_bridge_get_next_bridge() (drm-misc-next) 4. ✔ drm_for_each_bridge_in_chain() (drm-misc-next) 5. ✔ drm_bridge_connector_init (drm-misc-next) 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 removed bridges (drm-misc-next) 2. … handle gracefully atomic updates during bridge removal 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 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 --- Luca Ceresoli (4): 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 drivers/gpu/drm/drm_bridge.c | 6 ++++++ drivers/gpu/drm/sti/sti_hda.c | 5 +++++ drivers/gpu/drm/sti/sti_hdmi.c | 2 ++ 3 files changed, 13 insertions(+) --- base-commit: 0f2efbe6d8305b91c9b2c92ebaf8c24a614bc305 change-id: 20251003-b4-drm-bridge-alloc-add-before-attach-ef312c0b8a8c Best regards, -- Luca Ceresoli