linux-kernel - Re: [PATCH v5 1/8] usb: typec: Add default HPD device when register DisplayPort altmode

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Message-ID: <b0a41372-f28a-4e2f-9590-94fe2a86f7d8@rock-chips.com>
Date: Mon, 13 Oct 2025 09:31:03 +0800
From: Chaoyi Chen <chaoyi.chen@...k-chips.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
 Chaoyi Chen <kernel@...kyi.com>
Cc: 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>,
 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>,
 Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 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 v5 1/8] usb: typec: Add default HPD device when register
 DisplayPort altmode

On 10/12/2025 12:51 AM, Dmitry Baryshkov wrote:

> On Sat, Oct 11, 2025 at 11:32:26AM +0800, Chaoyi Chen wrote:
>> From: Chaoyi Chen <chaoyi.chen@...k-chips.com>
>>
>> Add default DRM AUX HPD bridge device when register DisplayPort
>> altmode. That makes it redundant for each Type-C driver to implement
>> a similar registration process in embedded scenarios.
>>
>> Signed-off-by: Chaoyi Chen <chaoyi.chen@...k-chips.com>
>> ---
>>
>> Changes in v5:
>> - Remove the calls related to `drm_aux_hpd_bridge_notify()`.
>> - Place the helper functions in the same compilation unit.
>> - Add more comments about parent device.
>>
>>   drivers/usb/typec/class.c         | 26 ++++++++++++++++++++++++++
>>   include/linux/usb/typec_altmode.h |  2 ++
>>   2 files changed, 28 insertions(+)
>>
>>   
>> +static void dp_altmode_hpd_device_register(struct typec_altmode *alt)
>> +{
>> +	if (alt->svid != USB_TYPEC_DP_SID)
>> +		return;
>> +
>> +	/*
>> +	 * alt->dev.parent->parent : USB-C controller device
>> +	 * alt->dev.parent         : USB-C connector device
>> +	 */
>> +	alt->hpd_dev = drm_dp_hpd_bridge_register(alt->dev.parent->parent,
>> +						  to_of_node(alt->dev.parent->fwnode));
> You can not do this, unless you make TYPEC core:
>
> depends on DRM || DRM=n
> select DRM_AUX_HPD_BRIDGE if DRM_BRIDGE && OF

You are right, Kconfig should be configured by the actual caller. Will fix in v6.


>
>> +	if (IS_ERR(alt->hpd_dev))
>> +		alt->hpd_dev = NULL;
>> +}
>> +
>>   static struct typec_altmode *
>>   typec_register_altmode(struct device *parent,
>>   		       const struct typec_altmode_desc *desc)

-- 
Best,
Chaoyi