linux-kernel - Re: [PATCH v2] drm/bridge: Fix assignment of the of

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Message-ID: <30fefafc-d19a-40cb-bcb1-3c586ba8e67e@linux.dev>
Date: Fri, 1 Nov 2024 11:49:07 +0800
From: Sui Jingfeng <sui.jingfeng@...ux.dev>
To: Johan Hovold <johan@...nel.org>
Cc: neil.armstrong@...aro.org, Andrzej Hajda <andrzej.hajda@...el.com>,
 Robert Foss <rfoss@...nel.org>,
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Abel Vesa <abel.vesa@...aro.org>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH v2] drm/bridge: Fix assignment of the of_node of the
 parent to aux bridge


On 2024/11/1 00:23, Johan Hovold wrote:
> On Thu, Oct 31, 2024 at 11:06:38PM +0800, Sui Jingfeng wrote:
>
>> But I think Johan do need more times to understand what exactly
>> the real problem is. We do need times to investigate new method.
> No, I know perfectly well what the (immediate) problem is here (I was
> the one adding support for the of_node_reused flag some years back).
>
> I just wanted to make sure that the commit message was correct and
> complete before merging (and also to figure out whether this particular
> patch needed to be backported).


Well under such a design, having the child device sharing the 'OF' device
node with it parent device means that one parent device can *only*
create one AUX bridge child device.

Since If you create two or more child AUX bridge, *all* of them will
call devm_drm_of_get_bridge(&auxdev->dev, auxdev->dev.of_node, 0, 0),
then we will *contend* the same next bridge resource.

Because of the 'auxdev->dev.of_node' is same for all its instance.
While other display bridges seems don't has such limitations.


> Johan

-- 
Best regards,
Sui