linux-kernel - [PATCH v4 6/8] usb: typec: Introduce mode

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Message-ID: <20260113130536.3068311-7-akuchynski@chromium.org>
Date: Tue, 13 Jan 2026 13:05:34 +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>,
	linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	chrome-platform@...ts.linux.dev
Cc: Tzung-Bi Shih <tzungbi@...nel.org>,
	Guenter Roeck <groeck@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
	Łukasz Bartosik <ukaszb@...omium.org>,
	Abel Vesa <abel.vesa@...aro.org>,
	Pooja Katiyar <pooja.katiyar@...el.com>,
	Johan Hovold <johan@...nel.org>,
	Hsin-Te Yuan <yuanhsinte@...omium.org>,
	Madhu M <madhu.m@...el.com>,
	Venkat Jayaraman <venkat.jayaraman@...el.com>,
	Andrei Kuchynski <akuchynski@...omium.org>
Subject: [PATCH v4 6/8] 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 d96ab106a980b..d185688a16b13 100644
--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -804,8 +804,10 @@ 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 6eadf7835f8f6..c4c5da6154da9 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 1fb5450c0a2f2..9b9254350733d 100644
--- a/drivers/usb/typec/class.c
+++ b/drivers/usb/typec/class.c
@@ -655,6 +655,7 @@ 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 dbb259d885266..d61ec38216fa9 100644
--- a/include/linux/usb/typec.h
+++ b/include/linux/usb/typec.h
@@ -155,6 +155,7 @@ 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 89b285a4ee7e6..4bde80e4c9b0b 100644
--- a/include/linux/usb/typec_altmode.h
+++ b/include/linux/usb/typec_altmode.h
@@ -37,6 +37,7 @@ struct typec_altmode {
 	u32				vdo;
 	unsigned int			active:1;
 	u8				priority;
+	bool			mode_selection;
 
 	char				*desc;
 	const struct typec_altmode_ops	*ops;
-- 
2.52.0.457.g6b5491de43-goog