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 3F6EAC61DD3 for ; Mon, 31 Aug 2026 10:04:26 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 3FF6D10E291; Mon, 31 Aug 2026 10:04:25 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="Synmpyxu"; 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 B5B0410E291 for ; Mon, 31 Aug 2026 10:04:23 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 99A2160120; Mon, 31 Aug 2026 10:04:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 230021F000E9; Mon, 31 Aug 2026 10:04:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788170662; bh=RtRPPMccgQ10Egkn46IrZlhGw9RDoAq0vmtTe4a5+m4=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=SynmpyxuJenWnR54J7UMgqDtYJ/EQYx4esovETq1vkZa2dLcf8wSxWtCSaoFlp8zL DNf9lQ7OXsWp8pINiRTe8Ohcy3Zn3tQY5Ifk/ff4AJlB7fF2J4yItDW+4NjEnuG95o ifOlUmU+HeMN2wgWE1JbmC+6mqPdCNvqHXVWPqYc8ngLrLgE/aGBbnSO1Zb8975vS1 gpLN9uCAPQy/Ys+gxEjw6eNgnKQwqJWZb9k5ZT6APEHGDdP9y/z29+YmzT9Ybi9ak+ Ln5ja1IxdRB4ZKuGAl00cMJ9Og3pYv8rqthGhSlTnKQvNCPcDppiYmldAdoUEihULJ 1sTJLF+O+LCmQ== From: sashiko-bot@kernel.org Subject: Re: [PATCH v6 27/29] drm/msm/dp: enable MST on capable sinks To: "Yongxing Mou" Cc: dri-devel@lists.freedesktop.org In-Reply-To: <20260831-msm-dp-mst-v6-27-c91d35d6fb9e@oss.qualcomm.com> References: <20260831-msm-dp-mst-v6-0-c91d35d6fb9e@oss.qualcomm.com> <20260831-msm-dp-mst-v6-27-c91d35d6fb9e@oss.qualcomm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Mon, 31 Aug 2026 10:04:21 +0000 Message-Id: <20260831100422.230021F000E9@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] Implicit boolean evaluation of enum drm_dp_mst_mode leads to incor= rectly enabling MST on SST-only sinks. -- commit c042ac1b2a4e178e7b21389f0bc30a1309bea2b3 Author: Abhinav Kumar drm/msm/dp: enable MST on capable sinks =20 MST topology discovery requires the sink to operate in MST mode. Enable MST on sinks that advertise MST capability and are connected to a multi-stream capable DP controller. > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp= /dp_display.c > index f350c1d03b06d..dbc0e82d333a5 100644 > --- a/drivers/gpu/drm/msm/dp/dp_display.c > +++ b/drivers/gpu/drm/msm/dp/dp_display.c [ ... ] > @@ -287,14 +311,17 @@ static int msm_dp_display_process_hpd_high(struct m= sm_dp_display_private *dp) > if (rc) > goto end; > =20 > - drm_edid =3D drm_edid_read_ddc(connector, &dp->aux->ddc); > - drm_edid_connector_update(connector, drm_edid); > + if (msm_dp_ctrl_get_stream_cnt(dp->ctrl) <=3D 1 || > + !drm_dp_read_mst_cap(dp->aux, dp->panel->dpcd)) { ^^^^ [Severity: High] Does this implicit boolean evaluation of the return value correctly handle SST-only sinks with sideband messaging? The drm_dp_read_mst_cap() function returns an enum drm_dp_mst_mode. If a si= nk returns DRM_DP_SST_SIDEBAND_MSG (which has a value of 2), the ! negation wi= ll evaluate to false. Will this cause the driver to incorrectly skip the neces= sary SST EDID read block here? > + drm_edid =3D drm_edid_read_ddc(connector, &dp->aux->ddc); > + drm_edid_connector_update(connector, drm_edid); > =20 > - if (!drm_edid) { > - DRM_ERROR("panel edid read failed\n"); > - /* check edid read fail is due to unplug */ > - if (!msm_dp_aux_is_link_connected(dp->aux)) > - return -ETIMEDOUT; > + if (!drm_edid) { > + DRM_ERROR("panel edid read failed\n"); > + /* check edid read fail is due to unplug */ > + if (!msm_dp_aux_is_link_connected(dp->aux)) > + return -ETIMEDOUT; > + } > } > =20 > msm_dp_link_process_request(dp->link); > @@ -316,6 +343,10 @@ static int msm_dp_display_process_hpd_high(struct ms= m_dp_display_private *dp) > */ > msm_dp_link_psm_config(dp->link, &dp->panel->link_info, false); > =20 > + if (msm_dp_ctrl_get_stream_cnt(dp->ctrl) > 1 && > + drm_dp_read_mst_cap(dp->aux, dp->panel->dpcd)) > + msm_dp_display_mst_enable(dp); ^^^^ [Severity: High] Similarly, will this cause DRM_DP_SST_SIDEBAND_MSG to be treated as fully MST capable? Since drm_dp_read_mst_cap() returns 2 for DRM_DP_SST_SIDEBAND_MSG, this condition evaluates to true. Could this lead to incorrectly executing msm_dp_display_mst_enable() to enable MST features on an SST sink, improper= ly writing DP_MST_EN to DP_MSTM_CTRL? > + > msm_dp_link_reset_phy_params_vx_px(dp->link); > =20 > end: --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260831-msm-dp-mst= -v6-0-c91d35d6fb9e@oss.qualcomm.com?part=3D27