linux-kernel - [PATCH RFC 3/8] usb: typec: Introduce mode

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Message-ID: <20251201122604.1268071-4-akuchynski@chromium.org>
Date: Mon,  1 Dec 2025 12:25:59 +0000
From: Andrei Kuchynski <akuchynski@...omium.org>
To: Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
	Benson Leung <bleung@...omium.org>,
	Jameson Thies <jthies@...gle.com>,
	Tzung-Bi Shih <tzungbi@...nel.org>,
	linux-usb@...r.kernel.org,
	chrome-platform@...ts.linux.dev
Cc: Guenter Roeck <groeck@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
	"Christian A. Ehrhardt" <lk@...e.de>,
	Abel Vesa <abel.vesa@...aro.org>,
	Pooja Katiyar <pooja.katiyar@...el.com>,
	Pavan Holla <pholla@...omium.org>,
	Madhu M <madhu.m@...el.com>,
	Venkat Jayaraman <venkat.jayaraman@...el.com>,
	linux-kernel@...r.kernel.org,
	Andrei Kuchynski <akuchynski@...omium.org>
Subject: [PATCH RFC 3/8] usb: typec: Introduce mode_selection bit

The port driver sets this bit for an alternate mode description to indicate
support for the mode selection feature. Once set, individual Alt Mode
drivers will no longer attempt to activate their respective modes within
their probe functions. This prevents race conditions and non-prioritized
activation.
The bit is not set by default. If left unset, the system retains the
current behavior where Alt Mode drivers manage their own activation logic.

Signed-off-by: Andrei Kuchynski <akuchynski@...omium.org>
---
 drivers/usb/typec/altmodes/displayport.c | 6 ++++--
 drivers/usb/typec/altmodes/thunderbolt.c | 2 +-
 drivers/usb/typec/class.c                | 1 +
 include/linux/usb/typec.h                | 1 +
 include/linux/usb/typec_altmode.h        | 1 +
 5 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
index 8d111ad3b71b..49d5a123e4c4 100644
--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -800,8 +800,10 @@ int dp_altmode_probe(struct typec_altmode *alt)
 	if (plug)
 		typec_altmode_set_drvdata(plug, dp);
 
-	dp->state = plug ? DP_STATE_ENTER_PRIME : DP_STATE_ENTER;
-	schedule_work(&dp->work);
+	if (!alt->mode_selection) {
+		dp->state = plug ? DP_STATE_ENTER_PRIME : DP_STATE_ENTER;
+		schedule_work(&dp->work);
+	}
 
 	return 0;
 }
diff --git a/drivers/usb/typec/altmodes/thunderbolt.c b/drivers/usb/typec/altmodes/thunderbolt.c
index 6eadf7835f8f..c4c5da6154da 100644
--- a/drivers/usb/typec/altmodes/thunderbolt.c
+++ b/drivers/usb/typec/altmodes/thunderbolt.c
@@ -307,7 +307,7 @@ static int tbt_altmode_probe(struct typec_altmode *alt)
 	typec_altmode_set_drvdata(alt, tbt);
 	typec_altmode_set_ops(alt, &tbt_altmode_ops);
 
-	if (tbt_ready(alt)) {
+	if (!alt->mode_selection && tbt_ready(alt)) {
 		if (tbt->plug[TYPEC_PLUG_SOP_P])
 			tbt->state = TBT_STATE_SOP_P_ENTER;
 		else if (tbt->plug[TYPEC_PLUG_SOP_PP])
diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
index 049d1829be98..cffe3c7d1671 100644
--- a/drivers/usb/typec/class.c
+++ b/drivers/usb/typec/class.c
@@ -639,6 +639,7 @@ typec_register_altmode(struct device *parent,
 	alt->adev.svid = desc->svid;
 	alt->adev.mode = desc->mode;
 	alt->adev.vdo = desc->vdo;
+	alt->adev.mode_selection = desc->mode_selection;
 	alt->roles = desc->roles;
 	alt->id = id;
 
diff --git a/include/linux/usb/typec.h b/include/linux/usb/typec.h
index 59d5fd7e4ff4..7a9dec9b0775 100644
--- a/include/linux/usb/typec.h
+++ b/include/linux/usb/typec.h
@@ -152,6 +152,7 @@ struct typec_altmode_desc {
 	/* Only used with ports */
 	enum typec_port_data	roles;
 	bool			inactive;
+	bool			mode_selection;
 };
 
 void typec_partner_set_pd_revision(struct typec_partner *partner, u16 pd_revision);
diff --git a/include/linux/usb/typec_altmode.h b/include/linux/usb/typec_altmode.h
index faf72e4d6ceb..c72065fddb7b 100644
--- a/include/linux/usb/typec_altmode.h
+++ b/include/linux/usb/typec_altmode.h
@@ -31,6 +31,7 @@ struct typec_altmode {
 	u32				vdo;
 	unsigned int			active:1;
 	u8				priority;
+	bool			mode_selection;
 
 	char				*desc;
 	const struct typec_altmode_ops	*ops;
-- 
2.52.0.158.g65b55ccf14-goog