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

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Message-ID: <4eizpzejw43gqt5jauvkeij65rracols2voa2osflwyjrwbvun@sovgqfuhg6mc>
Date: Sat, 11 Oct 2025 19:51:43 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: 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>,
        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 v5 1/8] usb: typec: Add default HPD device when register
 DisplayPort altmode

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

> +	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)

-- 
With best wishes
Dmitry