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

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Message-ID: <14b8ac71-489b-4192-92d6-5f228ff3881d@rock-chips.com>
Date: Thu, 23 Oct 2025 19:29:44 +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

Hi Heikki,

On 10/23/2025 4:45 PM, Heikki Krogerus wrote:
> On Thu, Oct 23, 2025 at 11:30:02AM +0800, Chaoyi Chen wrote:
>> From: Chaoyi Chen <chaoyi.chen@...k-chips.com>
>>
>> Several USB-C controller drivers have already implemented the DP HPD
>> bridge function provided by aux-hpd-bridge.c, but there are still
>> some USB-C controller driver that have not yet implemented it.
>>
>> This patch implements a generic DP HPD bridge based on aux-hpd-bridge.c,
>> so that other USB-C controller drivers don't need to implement it again.
>>
>> Signed-off-by: Chaoyi Chen <chaoyi.chen@...k-chips.com>
>> ---
>>   drivers/gpu/drm/bridge/Kconfig                | 11 ++++
>>   drivers/gpu/drm/bridge/Makefile               |  1 +
>>   .../gpu/drm/bridge/aux-hpd-typec-dp-bridge.c  | 51 +++++++++++++++++++
>>   3 files changed, 63 insertions(+)
>>   create mode 100644 drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c
>>
>> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
>> index b9e0ca85226a..9f31540d3ad8 100644
>> --- a/drivers/gpu/drm/bridge/Kconfig
>> +++ b/drivers/gpu/drm/bridge/Kconfig
>> @@ -33,6 +33,17 @@ config DRM_AUX_HPD_BRIDGE
>>   menu "Display Interface Bridges"
>>   	depends on DRM && DRM_BRIDGE
>>   
>> +config DRM_AUX_TYPEC_DP_HPD_BRIDGE
>> +	tristate "TypeC DP HPD bridge"
>> +	depends on DRM_BRIDGE && OF && TYPEC
>> +	select DRM_AUX_HPD_BRIDGE
>> +	help
>> +	  Simple USB Type-C DP bridge that terminates the bridge chain and
>> +	  provides HPD support.
>> +
>> +	  If the USB-C controller driver has not implemented this and you need
>> +	  the DP HPD support, say "Y" or "m" here.
> You don't need to depend on DRM_BRIDGE separately, but do you really
> need a separate module for this in the first place?
>
>>   config DRM_CHIPONE_ICN6211
>>   	tristate "Chipone ICN6211 MIPI-DSI/RGB Converter bridge"
>>   	depends on OF
>> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
>> index 245e8a27e3fc..e91736829167 100644
>> --- a/drivers/gpu/drm/bridge/Makefile
>> +++ b/drivers/gpu/drm/bridge/Makefile
>> @@ -1,6 +1,7 @@
>>   # SPDX-License-Identifier: GPL-2.0
>>   obj-$(CONFIG_DRM_AUX_BRIDGE) += aux-bridge.o
>>   obj-$(CONFIG_DRM_AUX_HPD_BRIDGE) += aux-hpd-bridge.o
>> +obj-$(CONFIG_DRM_AUX_TYPEC_DP_HPD_BRIDGE) += aux-hpd-typec-dp-bridge.o
> Instead, why not just make that a part of aux-hpd-bridge
> conditionally:
>
> ifneq ($(CONFIG_TYPEC),)
>          aux-hpd-bridge-y        += aux-hpd-typec-dp-bridge.o
> endif

Oh, I did consider that! But I noticed that aux-hpd-bridge.c contains the following statement module_auxiliary_driver(drm_aux_hpd_bridge_drv), which already includes a module_init. In the newly added file, in order to call the register function, another module_init was also added. If the two files are each made into a module separately, would there be a problem?


>
>
> thanks,
>
-- 
Best,
Chaoyi