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 920AB156654 for ; Tue, 25 Jun 2024 15:54:24 +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=1719330866; cv=none; b=tAh18doGFptIxE7VNtbG0XGOh+xfgahUrifPZiUSAYHBpgDgDUtGGdCQwYBmKSaiZN5lTAYNg4PdGjtyIx/r8nvK86V+C84KdKgrvgryV5iJQJozj9j7po43WxzaGEADim6d5eJLu1GOYaO2yfCDakysPZ5vCf8LfaUcKXrWYqI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719330866; c=relaxed/simple; bh=Eq5IeA6uv7y16NpA2G5zo9o5meWMdFkVmyr8Q/ABe8g=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=hcQ4p0/4qNIrbtEJ11Jjy2aAAMbnoXw4iJJBWYfrM8KyJdMz6btsTPyw3EHstvcv6PuLN00LjYW0lau39sHh1N+uO/TPcYgHkKzIHVOkiRM02u0iWkOqAQFxeIixTFP2EKzJUJpcUbz2aauvAnqpvhxEq/GR/xt08LiKaVv3+2s= 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=GxExNo0d; 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="GxExNo0d" Received: from pendragon.ideasonboard.com (unknown [193.209.96.36]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id A95C6BEB; Tue, 25 Jun 2024 17:53:59 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1719330839; bh=Eq5IeA6uv7y16NpA2G5zo9o5meWMdFkVmyr8Q/ABe8g=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=GxExNo0dNPRpKDk2Qr3lX2yE+lcxKySikvigTtQ9BBv3XAG5kK2cMk6/FitIxYCaP /E37Exn8j1SZbCYeb7H3ww13gNWyQsX1FleNzKW9AqV0POawC9g+xv6WlgTSCrBfCK TsIn99+WpVaQlnrNJh2dwkpIZOxY85TCmBsHzHfA= Date: Tue, 25 Jun 2024 18:54:01 +0300 From: Laurent Pinchart To: Sakari Ailus Cc: linux-media@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-sunxi@lists.linux.dev, Eugen Hristev , Maxime Ripard , Chen-Yu Tsai , Kieran Bingham , Tomi Valkeinen , Jacopo Mondi , Hans Verkuil Subject: Re: [PATCH 4/8] media: v4l2-subdev: Refactor warnings in v4l2_subdev_link_validate() Message-ID: <20240625155401.GD30459@pendragon.ideasonboard.com> References: <20240619012356.22685-1-laurent.pinchart+renesas@ideasonboard.com> <20240619012356.22685-5-laurent.pinchart+renesas@ideasonboard.com> <20240625140247.GC30459@pendragon.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: On Tue, Jun 25, 2024 at 03:46:06PM +0000, Sakari Ailus wrote: > Hi Laurent, > > On Tue, Jun 25, 2024 at 05:02:47PM +0300, Laurent Pinchart wrote: > > On Sat, Jun 22, 2024 at 04:47:33PM +0000, Sakari Ailus wrote: > > > Hi Laurent, > > > > > > Thanks for the patch. > > > > > > On Wed, Jun 19, 2024 at 04:23:52AM +0300, 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. > > > > > > > > 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() in this > > > > case to make sure that new offenders won't be introduced. > > > > > > > > Signed-off-by: Laurent Pinchart > > > > --- > > > > 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 4f71199bf592..2d5e39c79620 100644 > > > > --- a/drivers/media/v4l2-core/v4l2-subdev.c > > > > +++ b/drivers/media/v4l2-core/v4l2-subdev.c > > > > @@ -1451,11 +1451,15 @@ 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(!is_media_entity_v4l2_subdev(link->sink->entity))) > > > > + return -EINVAL; > > > > > > WARN*() is nowadays deprecated. > > > > Why so ? I've followed a recent discussion where some people pointed out > > they disliked WARN*() due to panic-on-warn, but I didn't see any > > conclusion there that deprecated WARN*(). > > Fair enough, there seems to have been more discussion. > > As this is still user-triggerable, this should be WARN_ON_ONCE() to prevent > the user from filling the logs, intentionally or not. It's user-triggerable, but only when the driver is clearly buggy :-) WARN_ON_ONCE() is OK with me though, I don't think warning every time would provide much added value. > > > Could you continue to use pr_warn_once() > > > for this (or dev_warn_one())? > > > > I think a WARN_ON() is the right option here. A failure indicates a > > clear driver bug, we should be as loud as possible to make sure it gets > > noticed during development. > > > > > > + > > > > + 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