From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0E14478C73 for ; Mon, 26 Aug 2024 12:05:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724673910; cv=none; b=KWJFr7j0Ig8UWf6mLpp2qTqyPDOJQOGrP4INTB2+SVJWs2xo1MW4RTW4ylvC1DcVR18Es8beNFv5BQQEPehm6Bytr9pPOe9zx49RsuKvY+VKHPJBBSY6DXX+PSdeMAM1FQwqYc0AcqsRi8kDAtjAJUsfqUmdDS7k07LhnDnzgxk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724673910; c=relaxed/simple; bh=4uDn1tuvtO4HsnO6l6017qHDCKJsSPGgFJFnhcjgzzo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Bjgjhpk+1wjVQ6nIk/YkVcwasJkiLXLh38dC6iZVnnWpmbgjZGsE7J6yOZ2B+TPXeL356eWebDRC0/qF87BCBfNwo09K4u1NzIJopGHsDJjhci8JSRhOOT2ElHxoJR2dSuoLQJZsoV5AQSWruXmsou9ZKvmaGrerlpiP6Hc+ggk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=N4OR7tvG; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="N4OR7tvG" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 4DAE96CA; Mon, 26 Aug 2024 14:04:00 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1724673840; bh=4uDn1tuvtO4HsnO6l6017qHDCKJsSPGgFJFnhcjgzzo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=N4OR7tvGX0wsgE3ic7wpYo7wg/VGxNnfvcMH3yYPIPl5iXw5NKdoHNP2BNI9X4u4e 7EixXW6Ek3qzYCb8bnrmmK8A8Q59qn00Cbf3u/THculVdHqnBs1PB8N0HvI3SJ1n3A gEGz3mV/fa3rGM7/+awiH0Ngezpl8p3qYw2K2Eic= Date: Mon, 26 Aug 2024 15:05:02 +0300 From: Laurent Pinchart To: Tomi Valkeinen Cc: linux-media@vger.kernel.org, Chen-Yu Tsai , Eugen Hristev , Hans Verkuil , Jacopo Mondi , Kieran Bingham , Maxime Ripard , Sakari Ailus , linux-renesas-soc@vger.kernel.org, linux-sunxi@lists.linux.dev Subject: Re: [PATCH v2 4/7] media: v4l2-subdev: Refactor warnings in v4l2_subdev_link_validate() Message-ID: <20240826120502.GB27785@pendragon.ideasonboard.com> References: <20240822154531.25912-1-laurent.pinchart+renesas@ideasonboard.com> <20240822154531.25912-5-laurent.pinchart+renesas@ideasonboard.com> Precedence: bulk X-Mailing-List: linux-sunxi@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Hi Tomi, On Mon, Aug 26, 2024 at 02:10:57PM +0300, Tomi Valkeinen wrote: > On 22/08/2024 18:45, Laurent Pinchart wrote: > > The v4l2_subdev_link_validate() function prints a one-time warning if it > > gets called on a link whose source or sink is not a subdev. As links get > > validated in the context of their sink, a call to the helper when the > > link's sink is not a subdev indicates that the driver has set its > > .link_validate() handler to v4l2_subdev_link_validate() on a non-subdev > > entity, which is a clear driver bug. On the other hand, the link's > > source not being a subdev indicates that the helper is used for a subdev > > connected to a video output device, which is a lesser issue, if only > > because this is currently common practice. > > Hmm, what does this mean... So we have a sink subdev, which might be > linked to a source subdev (in which case everything is fine), or it > might be linked to a non-subdev source. > > Why is it a bug to be linked to a non-subdev source? And if it is a bug, > why is ok (only pr_warn_once)? > > > There are no drivers left in the kernel that use > > v4l2_subdev_link_validate() in a context where it may get called on a > > non-subdev sink. Replace the pr_warn_once() with a WARN_ON_ONCE() in > > this case to make sure that new offenders won't be introduced. I'll add here A subsequent change will improve the v4l2_subdev_link_validate() helper to properly support validating video device to subdev links. > > > > Signed-off-by: Laurent Pinchart > > --- > > Changes since v1: > > > > - Switch from WARN_ON() to WARN_ON_ONCE() > > --- > > drivers/media/v4l2-core/v4l2-subdev.c | 14 +++++++++----- > > 1 file changed, 9 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c > > index 7c5812d55315..d3196042d5c5 100644 > > --- a/drivers/media/v4l2-core/v4l2-subdev.c > > +++ b/drivers/media/v4l2-core/v4l2-subdev.c > > @@ -1443,11 +1443,15 @@ int v4l2_subdev_link_validate(struct media_link *link) > > bool states_locked; > > int ret; > > > > - if (!is_media_entity_v4l2_subdev(link->sink->entity) || > > - !is_media_entity_v4l2_subdev(link->source->entity)) { > > - pr_warn_once("%s of link '%s':%u->'%s':%u is not a V4L2 sub-device, driver bug!\n", > > - !is_media_entity_v4l2_subdev(link->sink->entity) ? > > - "sink" : "source", > > + /* > > + * Links are validated in the context of the sink entity. Usage of this > > + * helper on a sink that is not a subdev is a clear driver bug. > > + */ > > + if (WARN_ON_ONCE(!is_media_entity_v4l2_subdev(link->sink->entity))) > > + return -EINVAL; > > + > > + if (!is_media_entity_v4l2_subdev(link->source->entity)) { > > + pr_warn_once("source of link '%s':%u->'%s':%u is not a V4L2 sub-device, driver bug!\n", > > link->source->entity->name, link->source->index, > > link->sink->entity->name, link->sink->index); > > return 0; -- Regards, Laurent Pinchart