Re: [PATCH v4 0/5] This series is split from the v15 "Add Type-C DP support for RK3399 EVB

From: Sebastian Reichel <sebastian.reichel@collabora.com>
To: Chaoyi Chen <chaoyi.chen@rock-chips.com>
Cc: "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>,
	"Luca Ceresoli" <luca.ceresoli@bootlin.com>,
	"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
	"Maxime Ripard" <mripard@kernel.org>,
	"Thomas Zimmermann" <tzimmermann@suse.de>,
	"David Airlie" <airlied@gmail.com>,
	"Simona Vetter" <simona@ffwll.ch>,
	"Sandy Huang" <hjc@rock-chips.com>,
	"Heiko Stübner" <heiko@sntech.de>,
	"Andy Yan" <andy.yan@rock-chips.com>,
	"Vinod Koul" <vkoul@kernel.org>,
	"Nicolas Frattaroli" <nicolas.frattaroli@collabora.com>,
	"Heikki Krogerus" <heikki.krogerus@linux.intel.com>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org,
	linux-phy@lists.infradead.org
Subject: Re: [PATCH v4 0/5] This series is split from the v15 "Add Type-C DP support for RK3399 EVB
Date: Tue, 28 Jul 2026 12:44:23 +0200	[thread overview]
Message-ID: <amh1sK_4KnD5zTlZ@venus> (raw)
In-Reply-To: <e22072d9-7fee-4f83-9ae9-5428e45c7507@rock-chips.com>

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Hello Chaoyi,

On Tue, Jul 28, 2026 at 10:33:48AM +0800, Chaoyi Chen wrote:
> >> Changes in v4:
> >> - Link to v3: https://lore.kernel.org/all/20260717072323.96-1-kernel@airkyi.com/
> >> - Scan the entire typec_bus and attempt to register the hpd bridge,
> >>   so as not to miss devices that were already added during initialization.
> > 
> > While that may help with the module being loaded late, it does not
> > help with triggering the module load in the first place.
> > 
> > The module does not have any MODULE_DEVICE_TABLE() helping with
> > that. So basically any system relying on the automatic hpd bridge
> > registration and using a modular kernel (e.g. the arm64 defconfig or
> > the kernels usually provided by Linux distributions) requires
> > manually loading that module to get any graphical output.
> >
> 
> Thank you for pointing this out. I will add it in v5.

Add what exactly? As this code is quite generic, you don't have
anything for a MODULE_DEVICE_TABLE() (i.e. no OF, no I2C, ...).

One solution I see to keep the notifier design would be to add

MODULE_SOFTDEP("pre: aux-hpd-typec-dp-bridge")

to some other module and piggy-back on it. Alternatively integrate
it directly to some other module, such as "drm_display_helper",
which already has DRM_DISPLAY_DP_HELPER and DRM_DISPLAY_DP_TUNNEL.
Adding TypeC DP AltMode as part of it seems sensible to me.

FWIW I suggest you test booting your patches work with the arm64
defconfig before your next submission ;)

Greetings,

-- Sebastian

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