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

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Message-ID: <aPoZhBdc1M6Qgfae@kuha.fi.intel.com>
Date: Thu, 23 Oct 2025 15:03:16 +0300
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: Chaoyi Chen <chaoyi.chen@...k-chips.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>,
	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

> > > 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?

You would not call module_init() from the new file. Instead you would
call drm_aux_hpd_typec_dp_bridge_init() and what ever directly from
aux-hpd-bridge.c:

diff --git a/drivers/gpu/drm/bridge/aux-bridge.h b/drivers/gpu/drm/bridge/aux-bridge.h
new file mode 100644
index 000000000000..ae689a7778fa
--- /dev/null
+++ b/drivers/gpu/drm/bridge/aux-hpd-bridge.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef AUX_HPD_BRIDGE_H
+#define AUX_HPD_BRIDGE_H
+
+#if IS_ENABLED(CONFIG_TYPEC)
+int drm_aux_hpd_typec_dp_bridge_init(void);
+void drm_aux_hpd_typec_dp_bridge_exit(void);
+#else
+static inline int drm_aux_hpd_typec_dp_bridge_init(void) { return 0; }
+static inline void drm_aux_hpd_typec_dp_bridge_exit(void) { }
+#endif /* IS_ENABLED(CONFIG_TYPEC) */
+
+#endif /* AUX_HPD_BRIDGE_H */
diff --git a/drivers/gpu/drm/bridge/aux-hpd-bridge.c b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
index 2e9c702c7087..3578df1df78a 100644
--- a/drivers/gpu/drm/bridge/aux-hpd-bridge.c
+++ b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
@@ -12,6 +12,8 @@
 #include <drm/drm_bridge.h>
 #include <drm/bridge/aux-bridge.h>
 
+#include "aux-hpd-bridge.h"
+
 static DEFINE_IDA(drm_aux_hpd_bridge_ida);
 
 struct drm_aux_hpd_bridge_data {
@@ -190,9 +192,16 @@ static int drm_aux_hpd_bridge_probe(struct auxiliary_device *auxdev,
 
        auxiliary_set_drvdata(auxdev, data);
 
+       drm_aux_hpd_typec_dp_bridge_init();
+
        return devm_drm_bridge_add(data->dev, &data->bridge);
 }
 
+static void drm_aux_hpd_bridge_remove(struct auxiliary_device *auxdev)
+{
+       drm_aux_hpd_typec_dp_bridge_exit();
+}
+
 static const struct auxiliary_device_id drm_aux_hpd_bridge_table[] = {
        { .name = KBUILD_MODNAME ".dp_hpd_bridge", .driver_data = DRM_MODE_CONNECTOR_DisplayPort, },
        {},
@@ -203,6 +212,7 @@ static struct auxiliary_driver drm_aux_hpd_bridge_drv = {
        .name = "aux_hpd_bridge",
        .id_table = drm_aux_hpd_bridge_table,
        .probe = drm_aux_hpd_bridge_probe,
+       .remove = drm_aux_hpd_bridge_remove,
 };
 module_auxiliary_driver(drm_aux_hpd_bridge_drv);


-- 
heikki