linux-kernel - [PATCH v1 2/2] usb: typec: altmodes/displayport: do not enter mode if port is the UFP

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Message-ID: <20250821203838.1721581-6-rdbabiera@google.com>
Date: Thu, 21 Aug 2025 20:38:35 +0000
From: RD Babiera <rdbabiera@...gle.com>
Cc: heikki.krogerus@...ux.intel.com, gregkh@...uxfoundation.org, 
	badhri@...gle.com, linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, 
	RD Babiera <rdbabiera@...gle.com>
Subject: [PATCH v1 2/2] usb: typec: altmodes/displayport: do not enter mode if
 port is the UFP

Nothing currently stops the DisplayPort Alt Mode driver from sending
Enter Mode if the port is the Data Device. Utilize
typec_altmode_get_data_role to prevent mode entry.

Signed-off-by: RD Babiera <rdbabiera@...gle.com>
---
 drivers/usb/typec/altmodes/displayport.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
index 1dcb77faf85d..8d111ad3b71b 100644
--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -758,7 +758,9 @@ int dp_altmode_probe(struct typec_altmode *alt)
 	struct fwnode_handle *fwnode;
 	struct dp_altmode *dp;
 
-	/* FIXME: Port can only be DFP_U. */
+	/* Port can only be DFP_U. */
+	if (typec_altmode_get_data_role(alt) != TYPEC_HOST)
+		return -EPROTO;
 
 	/* Make sure we have compatible pin configurations */
 	if (!(DP_CAP_PIN_ASSIGN_DFP_D(port->vdo) &
-- 
2.51.0.261.g7ce5a0a67e-goog