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 BCEEEC433EF for ; Thu, 7 Apr 2022 09:34:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243819AbiDGJg2 (ORCPT ); Thu, 7 Apr 2022 05:36:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243820AbiDGJg0 (ORCPT ); Thu, 7 Apr 2022 05:36:26 -0400 Received: from relay10.mail.gandi.net (relay10.mail.gandi.net [IPv6:2001:4b98:dc4:8::230]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 961C58F9A7 for ; Thu, 7 Apr 2022 02:34:26 -0700 (PDT) Received: (Authenticated sender: paul.kocialkowski@bootlin.com) by mail.gandi.net (Postfix) with ESMTPSA id 4F6FE240003; Thu, 7 Apr 2022 09:34:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1649324064; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=1QZGZ1l8/R6LZhl//SEGQRr/cjfdJ4XRWOzBWhSBo4I=; b=E0RlPrFXWSHAXPNxV2G21nu0veHQpr26sTTRKSYUb1XKBVxKJVi4xUpdsBFHnjoWGApEUC umKFnAhmhvCBpt+LvvamJ8rkTiq+WMqwcBagV2COABEPuDEcp23nx7LNZSQOjzZGqnzY3S XMZYEaIJAbX/azduTrkHP1SHWwxzGmG2iPmifpxpFjzUzNW3fZFyyBns7bRD8t4N0fhBDt RL2rsXPfW2eCcQbokZ/s0x2KwpEyG8zcv/JSPaTp4qJaI3a4aT2DtfnCD5HSOLqzqU8M83 v4oV3rOV13JSuHv6MsmVl/aIZhJc0HTie6N+OdeS7WQAb1ISSXkRUSWPvijwlA== From: Paul Kocialkowski To: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Paul Kocialkowski , Jagan Teki , Thomas Petazzoni , Bjorn Andersson , Thierry Reding , Linus Walleij Subject: [PATCH] drm: of: Improve error handling in bridge/panel detection Date: Thu, 7 Apr 2022 11:34:08 +0200 Message-Id: <20220407093408.1478769-1-paul.kocialkowski@bootlin.com> X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With the previous rework of drm_of_find_panel_or_bridge only -EPROBE_DEFER is returned while previous behavior allowed -ENODEV to be returned when the port/endpoint is either missing or unavailable. Make the default return code of the function -ENODEV to handle this and only return -EPROBE_DEFER in find_panel_or_bridge when the of device is available but not yet registered. Also return the error code whenever the remote node exists to avoid checking for child nodes. Checking child nodes could result in -EPROBE_DEFER returned by find_panel_or_bridge with an unrelated child node that would overwrite a legitimate -ENODEV from find_panel_or_bridge if the remote node from the of graph is unavailable. This happens because find_panel_or_bridge has no way to distinguish between a legitimate panel/bridge node that isn't yet registered and an unrelated node. Add comments around to clarify this behavior. Signed-off-by: Paul Kocialkowski Fixes: 67bae5f28c89 ("drm: of: Properly try all possible cases for bridge/panel detection") Cc: Bjorn Andersson Cc: Thierry Reding Cc: Linus Walleij --- drivers/gpu/drm/drm_of.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c index 8716da6369a6..97ea9d2016ff 100644 --- a/drivers/gpu/drm/drm_of.c +++ b/drivers/gpu/drm/drm_of.c @@ -223,6 +223,9 @@ static int find_panel_or_bridge(struct device_node *node, struct drm_panel **panel, struct drm_bridge **bridge) { + if (!of_device_is_available(node)) + return -ENODEV; + if (panel) { *panel = of_drm_find_panel(node); if (!IS_ERR(*panel)) @@ -265,7 +268,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np, struct drm_bridge **bridge) { struct device_node *node; - int ret; + int ret = -ENODEV; if (!panel && !bridge) return -EINVAL; @@ -282,8 +285,12 @@ int drm_of_find_panel_or_bridge(const struct device_node *np, ret = find_panel_or_bridge(node, panel, bridge); of_node_put(node); - if (!ret) - return 0; + /* + * If the graph/remote node is present we consider it + * to be the legitimate candidate here and return + * whatever code we got from find_panel_or_bridge. + */ + return ret; } } @@ -296,12 +303,18 @@ int drm_of_find_panel_or_bridge(const struct device_node *np, ret = find_panel_or_bridge(node, panel, bridge); of_node_put(node); - /* Stop at the first found occurrence. */ + /* + * Note that an unrelated (available) child node will cause + * find_panel_or_bridge to return -EPROBE_DEFER because there + * is no way to distinguish the node from a legitimate + * panel/bridge that didn't register yet. Keep iterating nodes + * and only return on the first found occurrence. + */ if (!ret) return 0; } - return -EPROBE_DEFER; + return ret; } EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge); -- 2.35.1