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 45B45C5320E for ; Mon, 19 Aug 2024 11:38:50 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id BD62F10E249; Mon, 19 Aug 2024 11:38:49 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=bootlin.com header.i=@bootlin.com header.b="aL5nPNyw"; dkim-atps=neutral Received: from relay6-d.mail.gandi.net (relay6-d.mail.gandi.net [217.70.183.198]) by gabe.freedesktop.org (Postfix) with ESMTPS id 17F6D10E249 for ; Mon, 19 Aug 2024 11:38:47 +0000 (UTC) Received: by mail.gandi.net (Postfix) with ESMTPSA id C9DF1C0003; Mon, 19 Aug 2024 11:38:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1724067525; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vi25+xcJfrO7nLXZ6nqh00qEFioKK3pAMkYDoRraxek=; b=aL5nPNyweFQC+1Fdl4ZDP+opbjLoTmuAsy8mnCool/vUtMrQT0y+vmzoC9r1P1IYhRiqAi foCJyBdjyU5EqLcn8XyjMO658Ms4PTiQdWUBUYy6m137yHqFLlyMtSmIW4myg6SiyJr/Dn Y/2gq2tQHF4qbR4PYhqEgzy6quBQP/Pw0ARmVnpAp8h5x92ue/bz+EBlEfnhx+ZHpjxceo s6XXVyF+zabBgn54ztcM3O/MAuWA2Je4YnLsrUI22Dqw6LHKW3KOYtfX5DJ1uqPAVmNXL6 COKvHNJl/AvfMMqBTtGKwUFhUuGb8Zc75xZdE+gXM6rZFgqp2/0fw7Jf/coyCQ== Date: Mon, 19 Aug 2024 13:38:40 +0200 From: Luca Ceresoli To: Andi Shyti Cc: Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Thomas Petazzoni , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drm/bridge: ti-sn65dsi83: use dev_err_probe when failing to get panel bridge Message-ID: <20240819133840.26045152@booty> In-Reply-To: References: <20240808-ti-sn65dsi83-dev_err_probe-v1-1-72417aa275ab@bootlin.com> <20240813101643.5bf8d245@booty> Organization: Bootlin X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-GND-Sasl: luca.ceresoli@bootlin.com 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: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hello Andi, thanks for your additional comments. On Tue, 13 Aug 2024 16:32:50 +0200 Andi Shyti wrote: > Hi Luca, > > On Tue, Aug 13, 2024 at 10:16:43AM +0200, Luca Ceresoli wrote: > > On Thu, 8 Aug 2024 11:35:23 +0100 > > Andi Shyti wrote: > > > On Thu, Aug 08, 2024 at 12:26:14PM +0200, Luca Ceresoli wrote: > > > > When devm_drm_of_get_bridge() fails, the probe fails silently. Use > > > > dev_err_probe() instead to log an error or report the deferral reason, > > > > whichever is applicable. > > > > > > > > Signed-off-by: Luca Ceresoli > > > > --- > > > > drivers/gpu/drm/bridge/ti-sn65dsi83.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c > > > > index 57a7ed13f996..60b9f14d769a 100644 > > > > --- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c > > > > +++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c > > > > @@ -606,7 +606,7 @@ static int sn65dsi83_parse_dt(struct sn65dsi83 *ctx, enum sn65dsi83_model model) > > > > > > > > panel_bridge = devm_drm_of_get_bridge(dev, dev->of_node, 2, 0); > > > > if (IS_ERR(panel_bridge)) > > > > - return PTR_ERR(panel_bridge); > > > > + return dev_err_probe(dev, PTR_ERR(panel_bridge), "Failed to get panel bridge\n"); > > > > > > patch looks good, but the message is a bit misleading. You are > > > not failing to get the panel bridge, but you are failing to find > > > a panel bridge in a DT node. Right? > > > > As I can see from both the documentation and the code, > > devm_drm_of_get_bridge() is really returning a pointer to a panel > > bridge, potentially allocating and adding it in case it was not present > > before. Navigating the device tree is only a part of what it does. > > > > Do you think I am missing something? > > No, maybe it's me being a bit pedantic. In the sense that we are > not really failing to get the panel, but most probably the panel > is not installed. The panels I'm used to, which I believe to be the most common in embedded systems just have no way of being detected, so the operating system cannot detect a "panel not installed" condition. However I went back to the code and realized your initial remark ("you are failing to find a panel bridge in a DT node") is more correct than I initially thought. Indeed there are two failure reasons for devm_drm_of_get_bridge() to fail: DT lookup and panel bridge creation failures. The latter however can be due to -ENOMEM (unlikely) or (panel->connector_type == DRM_MODE_CONNECTOR_Unknown), which in turn can be due to either a panel driver error or again a DT error in case the driver gets the panel type from DT, as panel-simple.c does. That said, the role of devm_drm_of_get_bridge() is to provide a panel bridge object. If it fails, that means it is unable to provide such an object for whatever reason. Reasons currently include DT issues (the most likely), driver bug and -ENOMEM. There could be more reasons in future versions of the implementation. I'm afraid I'm unable to express all the above logic in a single commit title line. However, should you have a better commit title or message to suggest, I'm still open to improvements. I value good commit messages. > I'm not strong on this comment, though, so that > feel free to add: > > Reviewed-by: Andi Shyti Otherwise, I'm sending v2 with your review tag by the end of the week. Luca -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com