Re: [PATCH 00/10] Synopsys DisplayPort Controller improvements for Rockchip platforms

From: Sebastian Reichel <sebastian.reichel@collabora.com>
To: Chaoyi Chen <kernel@airkyi.com>
Cc: "Sandy Huang" <hjc@rock-chips.com>,
	"Heiko Stübner" <heiko@sntech.de>,
	"Andy Yan" <andy.yan@rock-chips.com>,
	"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
	"Maxime Ripard" <mripard@kernel.org>,
	"Thomas Zimmermann" <tzimmermann@suse.de>,
	"Andrzej Hajda" <andrzej.hajda@intel.com>,
	"Neil Armstrong" <neil.armstrong@linaro.org>,
	"Robert Foss" <rfoss@kernel.org>,
	"Laurent Pinchart" <Laurent.pinchart@ideasonboard.com>,
	"Jonas Karlman" <jonas@kwiboo.se>,
	"Jernej Skrabec" <jernej.skrabec@gmail.com>,
	"Rob Herring" <robh@kernel.org>,
	"Krzysztof Kozlowski" <krzk+dt@kernel.org>,
	"Conor Dooley" <conor+dt@kernel.org>,
	"Damon Ding" <damon.ding@rock-chips.com>,
	"Dmitry Baryshkov" <lumag@kernel.org>,
	"Alexey Charkov" <alchark@gmail.com>,
	dri-devel@lists.freedesktop.org,
	linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org,
	devicetree@vger.kernel.org, kernel@collabora.com
Subject: Re: [PATCH 00/10] Synopsys DisplayPort Controller improvements for Rockchip platforms
Date: Mon, 30 Mar 2026 13:50:43 +0200	[thread overview]
Message-ID: <acphlgK6ZmBitGJL@venus> (raw)
In-Reply-To: <FE1BFB774BE13241+54b8a8ce-5a8c-495d-a53f-65a2440924fb@airkyi.com>

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Hello Chaoyi,

On Mon, Mar 30, 2026 at 09:34:15AM +0800, Chaoyi Chen wrote:
> > There are two parts, which possibly need some discussion:
> > 
> >  1. I added a dedicated bridge callback for out-of-band hotplug events,
> >     which is separate from the hotplug_notify. I have a feeling, that
> >     there might be a better solution, but haven't found it.
> 
> Could you explain what an out-of-band hotplug event is?
> 
> Can't the drivers/usb/typec/altmodes/displayport.c respond to these
> hot-plug events? Thank you.

That is what generates the out-of-band hotplug event in the first
place via drm_connector_oob_hotplug_event(). The oob in that call
means out of band.

If you look at that function it calls oob_hotplug_event() callback
on the DRM connector, which is then implemented by
drm_bridge_connector_oob_hotplug_event(). This function calls uses
the normal hpd handling (shared by in-band and out-of-band) and I'm
patching it, so that the bridges are aware of hpd explicitly being
provided out-of-band.

Greetings,

-- Sebastian

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