linux-kernel - Re: [PATCH v7 2/9] drm/bridge: Implement generic USB Type-C DP HPD bridge

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Message-ID: <836a096a-c6ed-4c9c-9de5-f8b0ee44fac3@rock-chips.com>
Date: Fri, 24 Oct 2025 16:16:00 +0800
From: Chaoyi Chen <chaoyi.chen@...k-chips.com>
To: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Vinod Koul <vkoul@...nel.org>,
 Kishon Vijay Abraham I <kishon@...nel.org>, Heiko Stuebner
 <heiko@...ech.de>, Sandy Huang <hjc@...k-chips.com>,
 Andy Yan <andy.yan@...k-chips.com>,
 Yubing Zhang <yubing.zhang@...k-chips.com>,
 Frank Wang <frank.wang@...k-chips.com>,
 Andrzej Hajda <andrzej.hajda@...el.com>,
 Neil Armstrong <neil.armstrong@...aro.org>, 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>,
 Amit Sunil Dhamne <amitsd@...gle.com>,
 Chaoyi Chen <chaoyi.chen@...k-chips.com>, Dragan Simic <dsimic@...jaro.org>,
 Johan Jonker <jbx6244@...il.com>, Diederik de Haas <didi.debian@...ow.org>,
 Peter Robinson <pbrobinson@...il.com>, linux-usb@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-phy@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v7 2/9] drm/bridge: Implement generic USB Type-C DP HPD
 bridge

On 10/24/2025 4:01 PM, Heikki Krogerus wrote:

> On Thu, Oct 23, 2025 at 11:30:02AM +0800, Chaoyi Chen wrote:
>> +static int drm_typec_bus_event(struct notifier_block *nb,
>> +			       unsigned long action, void *data)
>> +{
>> +	struct typec_altmode *alt = (struct typec_altmode *)data;
>> +
>> +	if (action != TYPEC_ALTMODE_REGISTERED)
>> +		goto done;
>> +
>> +	if (alt->svid != USB_TYPEC_DP_SID)
>> +		goto done;
>> +
>> +	/*
>> +	 * alt->dev.parent->parent : USB-C controller device
>> +	 * alt->dev.parent         : USB-C connector device
>> +	 */
>> +	drm_dp_hpd_bridge_register(alt->dev.parent->parent,
>> +				   to_of_node(alt->dev.parent->fwnode));
> Okay, this explains it. So you do need the port altmode.
>
> So you'll need to export the device types and check that the parent of
> the altmode is the port instead of partner.
>
>          if (!is_typec_port(alt->dev.parent) || alt->svid != USB_TYPEC_DP_SID)
>                  return NOTIFY_DONE;
>
> I think we might as well export all the types while at it. Check the
> attachment.

Oh, I did miss the existence of partner. Thank you for your code!


>
> thanks,
>
-- 
Best,
Chaoyi