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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0CD95CE79AF for ; Wed, 20 Sep 2023 08:24:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233686AbjITIY6 (ORCPT ); Wed, 20 Sep 2023 04:24:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38682 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233899AbjITIY4 (ORCPT ); Wed, 20 Sep 2023 04:24:56 -0400 Received: from madras.collabora.co.uk (madras.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e5ab]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8F988131 for ; Wed, 20 Sep 2023 01:24:44 -0700 (PDT) Received: from [192.168.1.100] (2-237-20-237.ip236.fastwebnet.it [2.237.20.237]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) (Authenticated sender: kholk11) by madras.collabora.co.uk (Postfix) with ESMTPSA id 447F566003AF; Wed, 20 Sep 2023 09:24:42 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1695198283; bh=A5e7XZz1Vz5cGVbLdkx/jRxgzoIVS2ZgkuULWqKvE0Y=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=FsZTDG4RTKeQAaMJvZSgnuAAHZHNvMI0PvMF3quOB72278UF5mqcvnTLhBRw0fDN/ OpDihFI2OsXEwyql6hveCMhCqqyzEyGyjl1OKbMAGbQ4zpTcfPz2xXV9LzESsQMW/7 Qw7Fkepm4uuTA/YmzQYVJn0uX5xAeAEdas5hcHipKH6eLRiUNSBMUDaPzRT3eqMhD5 WAiJcwytHOg93mEhZbvCLMnQp/nb1BdhC6HOaF9jnH5ErC4q/7QT6pG3UAV8D0SvRF Ea16ix2fzDBs1m+m/5VwS6jA/eCiQPUrYKQLbbCdnLdGwJvz+v9fZESf/yzaDg3cXK oZNztHAHPPiwA== Message-ID: <6cde344a-9e93-07b0-862b-aa401e6c64fb@collabora.com> Date: Wed, 20 Sep 2023 10:24:39 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.0 Subject: Re: [PATCH] drm/bridge: panel: Fix device link for DRM_BRIDGE_ATTACH_NO_CONNECTOR Content-Language: en-US To: Ying Liu , "andrzej.hajda@intel.com" Cc: "neil.armstrong@linaro.org" , "rfoss@kernel.org" , "Laurent.pinchart@ideasonboard.com" , "jonas@kwiboo.se" , "jernej.skrabec@gmail.com" , "airlied@gmail.com" , "daniel@ffwll.ch" , "ulf.hansson@linaro.org" , "dri-devel@lists.freedesktop.org" , "linux-kernel@vger.kernel.org" , "kernel@collabora.com" , "ehristev@collabora.com" , "wenst@chromium.org" References: <20230918150043.403250-1-angelogioacchino.delregno@collabora.com> From: AngeloGioacchino Del Regno In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 19/09/23 03:45, Ying Liu ha scritto: > Hi Angelo, > > Thank you for the patch. > > On Monday, September 18, 2023 11:01 PM, AngeloGioacchino Del Regno wrote: >> When external bridges are attached with >> DRM_BRIDGE_ATTACH_NO_CONNECTOR, >> the panel bridge may also get the same flag, but in the .attach() >> callback for the panel bridge a device link is added only when this >> flag is not present; To make things worse, the .detach() callback >> tries to delete the device link unconditionally and without checking >> if it was created in the first place, crashing the kernel with a NULL >> pointer kernel panic upon calling panel_bridge_detach(). >> >> Fix that by moving the device_link_add() call before checking if the >> DRM_BRIDGE_ATTACH_NO_CONNECTOR flag is present. >> >> Fixes: 199cf07ebd2b ("drm/bridge: panel: Add a device link between drm >> device and panel device") >> Signed-off-by: AngeloGioacchino Del Regno >> >> --- >> drivers/gpu/drm/bridge/panel.c | 16 ++++++++-------- >> 1 file changed, 8 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/gpu/drm/bridge/panel.c >> b/drivers/gpu/drm/bridge/panel.c >> index e00d2e94c751..8c507dfd589e 100644 >> --- a/drivers/gpu/drm/bridge/panel.c >> +++ b/drivers/gpu/drm/bridge/panel.c >> @@ -67,14 +67,6 @@ static int panel_bridge_attach(struct drm_bridge >> *bridge, >> struct drm_device *drm_dev = bridge->dev; >> int ret; >> >> - if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) >> - return 0; >> - >> - if (!bridge->encoder) { >> - DRM_ERROR("Missing encoder\n"); >> - return -ENODEV; >> - } >> - >> panel_bridge->link = device_link_add(drm_dev->dev, panel->dev, >> DL_FLAG_STATELESS); >> if (!panel_bridge->link) { >> @@ -83,6 +75,14 @@ static int panel_bridge_attach(struct drm_bridge >> *bridge, >> return -EINVAL; >> } >> >> + if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) >> + return 0; >> + >> + if (!bridge->encoder) { >> + DRM_ERROR("Missing encoder\n"); > > Shouldn't the device link be deleted in case of error? > Whoops! Yes, that's right. I'm sending a v2 right now. Thanks! Angelo > Regards, > Liu Ying > >> + return -ENODEV; >> + } >> + >> drm_connector_helper_add(connector, >> &panel_bridge_connector_helper_funcs); >> >> -- >> 2.42.0 >