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 629602FB0B8 for ; Mon, 15 Sep 2025 10:14:04 +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=1757931247; cv=none; b=KBqp/0pAvMeJBVtqir4QmU17n8iRoVFDtGkqqeQnGiL3M4iVda+GdjcoNsOvCzztvrFhh8J1PulVulMvRFjf9irW+a86yBsNGBooyMrC6eKBS3SMkq2fB8nYltkF6/0TYrgR5FNW/i/V5Nn/pm7dfrUH3vA6+gt94KVtTtOcEFI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757931247; c=relaxed/simple; bh=1FfJlSkjW9D2AOl6ceSDBmCqqwtKCg+82tzd0KTGIvk=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=Fjc05I0SijJsgs46mPR/ECWtCglrjZzYbfx14x8dbC9qEh5VT2oIrCnoqLEASxSqRVdmHaJlAw6p5XOHAI6jwQaFv3c/XhsFiUnJgzGz1iiigF3kL0aBfCGKZS6tacDhgSTrn9UGTNmpN8MD0yltPQAERUp+PnzlWRxEINgorr0= 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=gSzJDiXB; 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="gSzJDiXB" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-04.galae.net (Postfix) with ESMTPS id D1241C6B399; Mon, 15 Sep 2025 10:13:45 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id 0491F6063F; Mon, 15 Sep 2025 10:14:02 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 7526C102F2AA2; Mon, 15 Sep 2025 12:13:47 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1757931240; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding; bh=ClgjtsTa+fjb0PUWeFBk56M8yGoBllTGlfLie6WA88E=; b=gSzJDiXBgTlxZCdVMadgiYCy81b2QDR7BjERq14Ho2oRJniBwV7alxdJdLRufitoTXem3+ XoZVRJSLtgIOg3k5j45NDUBG6HHD+iJ1LravybZSyVAgxwbcvIO/bWNE2Qs2m3LoEeGLKI 5rTCFWgGRMDLlY/oQ3nFrwVkMkHbMjxkkJ+tQ0oi/XdrXgNuS98XriuUqkf4zmPbDxFEps VeSfHeMuNwBbBoow+ZOmx3u3DZdaOxvb2aJ0Yb+cJcZ3N0KqDr3bT+GrW12+vmxT3EJd2n soM4fz6OPESSy0pho/drROUJhyCgTIyQ/fu0UZ5qJE9OT+6pC9PnxWCsv2pvfQ== From: Luca Ceresoli Subject: [PATCH v9 0/3] drm/bridge: debugfs: show refcount and list removed bridges Date: Mon, 15 Sep 2025 12:12:45 +0200 Message-Id: <20250915-drm-bridge-debugfs-removed-v9-0-6e5c0aff5de9@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=H4sIAJ3mx2gC/32P22rEIBCGXyV4XYuag5qrvkcpi4cxEZK4a4y0L Hn3mmyh7M3eDPwz8M3339EK0cOK+uqOImS/+rCUIN8qZEa1DIC9LRkxwlrSEIFtnLGO3paLBb0 NbsUR5pDBYtZy6YRk0OgaFcA1gvPfJ/zz65Ej3LbyIz2WSKsVsAnz7FNfMcsctYY3xmmtGyGpE s52XUeYNJ0zIFmZzh7oU4fTJx01TcHgAdJ1S9iFeAFlxsvf0dGGKqBcd63qM0OHz+jXFOLP2T3 zU+jkCipf1cwcEyw54eQoLLn40CGkyS/vpckJzuIfJil7CRMF1pq6toIbo9v2Gbbv+y8lj3djo wEAAA== X-Change-ID: 20250408-drm-bridge-debugfs-removed-2579f892e4b3 To: Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter Cc: Hui Pu , Thomas Petazzoni , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Luca Ceresoli , Dmitry Baryshkov X-Mailer: b4 0.14.2 X-Last-TLS-Session-Version: TLSv1.3 This series shows removed bridges to the global /dri/bridges file. Removed bridges are bridges after drm_bridges_remove() but before they are eventually freed on the last drm_bridge_put(). 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 [1]. Here's the work breakdown (➜ marks the current series): 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 [1]. 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-rc1) C. ✔ kunit tests (v6.17-rc1) D. ✔ add get/put to drm_bridge_add/remove() + attach/detach() and warn on old allocation pattern (v6.17-rc1) 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() (partially in drm-misc-next) 4. …✔ drm_for_each_bridge_in_chain() (partially in drm-misc-next) 5. drm_bridge_connector_init 6. of_drm_find_bridge 7. drm_of_find_panel_or_bridge, *_of_get_bridge F. ➜ debugfs improvements 1. ✔ add top-level 'bridges' file (v6.16) 2. ➜ show refcount and list removed bridges 2. … handle gracefully atomic updates during bridge removal 3. … DSI host-device driver interaction 4. finish the hotplug bridge work, removing the "always-disconnected" connector, moving code to the core and potentially removing the hotplug-bridge itself (this needs to be clarified as points 1-3 are developed) To show the removed bridges we need to keep track of them, thus add a new global list to store them between drm_bridge_remove() and the eventual free. This is bit tricky in case a bridge is removed and then re-added before being freed. This is handled in patch 2. This series depends on one other series: * [PATCH v2 0/9] drm/bridge: get/put the bridge when looping over the encoder chain Link: https://lore.kernel.org/r/20250808-drm-bridge-alloc-getput-for_each_bridge-v2-0-edb6ee81edf1@bootlin.com Reason: trivial conflict in context (drm_for_each_bridge_in_chain_scoped()) [0] https://gitlab.freedesktop.org/drm/misc/kernel/-/commit/0cc6aadd7fc1e629b715ea3d1ba537ef2da95eec [1] https://lore.kernel.org/lkml/20250206-hotplug-drm-bridge-v6-0-9d6f2c9c3058@bootlin.com/t/#u Signed-off-by: Luca Ceresoli --- Changes in v9: - Renamed leftover instances of "removed" to "lingering" - Added Maxime R-by - Link to v8: https://lore.kernel.org/r/20250912-drm-bridge-debugfs-removed-v8-0-5c33d87ccb55@bootlin.com Changes in v8: - Removed patch 1, now in drm-misc-next - Renamed "removed" -> "lingering" - Rewrote documentation changes to use "register" in lieu of "publish", split them to a separate patch - Link to v7: https://lore.kernel.org/r/20250819-drm-bridge-debugfs-removed-v7-0-970702579978@bootlin.com This series was initially part of v6 of this other series: - Link to v6: https://lore.kernel.org/dri-devel/20250206-hotplug-drm-bridge-v6-0-9d6f2c9c3058@bootlin.com/ --- Luca Ceresoli (3): drm/bridge: add list of removed refcounted bridges drm/debugfs: show lingering bridges drm/bridge: adapt drm_bridge_add/remove() docs, mention the lingering list drivers/gpu/drm/drm_bridge.c | 46 ++++++++++++++++++++++++++++++++++++-------- 1 file changed, 38 insertions(+), 8 deletions(-) --- base-commit: 2d2f1dc74cfbbb4891a8fd666029c6fce926fcfd change-id: 20250408-drm-bridge-debugfs-removed-2579f892e4b3 Best regards, -- Luca Ceresoli