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 0E6A1C982D0 for ; Thu, 17 Sep 2026 08:17:16 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 35EC610E68E; Thu, 17 Sep 2026 08:17:15 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="ZQZXFoeS"; dkim-atps=neutral Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by gabe.freedesktop.org (Postfix) with ESMTPS id 698F110E68E for ; Thu, 17 Sep 2026 08:17:13 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 459C5600D4; Thu, 17 Sep 2026 08:17:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C749E1F00893; Thu, 17 Sep 2026 08:17:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789633032; bh=NWvyGveb+McTgJMo8EjKDgd0rD3pwid9BPHqVHpsiy4=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=ZQZXFoeSQM7bmt3ZBymXP2VQWeTvswfsfM0lly+krlaMAZnw06qpR+FAbBGvNuUYM SRw1Yq00M5Y4j3reVLI+Fr2PMnxAESSEQDtvbxTga5KWXCEPv+jeMBfaeuZbtoyQHU 6QbGx56Nn3fGG6BrL4p/Ur12GpUIutGdYfasDh8bWhxyM97KoGTDRa5i1jsHfYE7dP aodXbiE64s5E6M8v6h7O1huG71KHRIk9TMbSxgDlRHYJ1wcYCzdqCWmLfauoSD5ow6 XgfOurRE59D242z/U54y8PWqtPQUGn3JXhPcTzBK6F1m4Vf1+mOOHEqfDyeZaJqu8B y4gHdMNH7SafQ== From: sashiko-bot@kernel.org Subject: Re: [PATCH] drm/dp/mst: skip connector creation for unplugged downstream ports To: "Xiao Lu" Cc: dri-devel@lists.freedesktop.org In-Reply-To: <20260917080126.1729898-1-xiaolu.xie@intel.com> References: <20260917080126.1729898-1-xiaolu.xie@intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Thu, 17 Sep 2026 08:17:11 +0000 Message-Id: <20260917081711.C749E1F00893@smtp.kernel.org> 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: , Reply-To: sashiko-reviews@lists.linux.dev Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: - [High] drm/dp/mst: missing connector creation breaks hotplug for empty do= wnstream ports -- commit b7642d2c459f1deba3af19a444979a2c15cbf1e0 Author: Xiao Lu drm/dp/mst: skip connector creation for unplugged downstream ports This patch modifies the MST link enumeration path to skip creating DRM connectors for downstream ports that do not have a device connected. It aims to reduce error log noise and spurious sideband messages from DPCD reads on empty ports. > diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/= drm/display/drm_dp_mst_topology.c > --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c > +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c > @@ -2448,7 +2448,7 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_m= st_branch *mstb, > =20 > if (port->connector) > drm_modeset_unlock(&mgr->base.lock); > - else if (!port->input) > + else if (!port->input && port->ddps) > drm_dp_mst_port_add_connector(mstb, port); [Severity: High] If we skip connector creation here for empty ports, will the hotplug path actually create the connector when a monitor is plugged in? Looking at drm_dp_mst_handle_conn_stat(), create_connector is only set to true when transitioning from an input port to an output port: } else if (port->input && !conn_stat->input_port) { create_connector =3D true; For standard downstream ports, port->input is 0, so create_connector remains false during a hotplug event. Later in drm_dp_mst_handle_conn_stat(), it checks: else if (create_connector) drm_dp_mst_port_add_connector(mstb, port); Since create_connector evaluated to false, the dynamic connector creation is bypassed. Also, drm_dp_port_set_pdt() returns 0 for regular SST monitors: if (drm_dp_mst_is_end_device(port->pdt, port->mcs)) { /* add i2c over sideband */ ret =3D drm_dp_mst_register_i2c_bus(port); This prevents the caller from setting dowork =3D true and triggering a fallback link address reprobe. Does this mean a display plugged into an MST hub port that was empty at boot will remain permanently dark because its DRM connector is never created? --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260917080126.1729= 898-1-xiaolu.xie@intel.com?part=3D1