linux-kernel - [PATCH RFC] usb: typec: thunderbolt: Fix Thunderbolt adapter type bitfield values

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Message-Id: <20250926-topic-tbt_header_bit_fix-v1-1-122238af5c82@oss.qualcomm.com>
Date: Fri, 26 Sep 2025 14:32:57 +0200
From: Konrad Dybcio <konradybcio@...nel.org>
To: Heikki Krogerus <heikki.krogerus@...ux.intel.com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Benson Leung <bleung@...omium.org>, 
 Abhishek Pandit-Subedi <abhishekpandit@...omium.org>, 
 Jameson Thies <jthies@...gle.com>, 
 Andrei Kuchynski <akuchynski@...omium.org>, 
 Tzung-Bi Shih <tzungbi@...nel.org>, Guenter Roeck <groeck@...omium.org>
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, 
 chrome-platform@...ts.linux.dev, 
 Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: [PATCH RFC] usb: typec: thunderbolt: Fix Thunderbolt adapter type
 bitfield values

From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>

The value has been amended with the release of the USB Type-C
Specification v2.1, reportedly as an erratum.

Signed-off-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
---
I bundled a change to the CrOS EC driver based on the assumption that
it worked around the faulty definition. I see the Intel PMC mux driver
also checks for this bit, but it seems like that driver assumes that
the value is in-spec (i.e. it may be buggy as of right now).

Adding the respective maintainers to make sure everyone can see this.
---
 drivers/platform/chrome/cros_ec_typec.c | 2 +-
 include/linux/usb/typec_tbt.h           | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
index b712bcff6fb2674ec79286159090df6d79b32e9a..d80f3de1b87c362a2825bd19f826c5be077583aa 100644
--- a/drivers/platform/chrome/cros_ec_typec.c
+++ b/drivers/platform/chrome/cros_ec_typec.c
@@ -585,7 +585,7 @@ static int cros_typec_enable_tbt(struct cros_typec_data *typec,
 	data.device_mode = TBT_MODE;
 
 	if (pd_ctrl->control_flags & USB_PD_CTRL_TBT_LEGACY_ADAPTER)
-		data.device_mode = TBT_SET_ADAPTER(TBT_ADAPTER_TBT3);
+		data.device_mode = TBT_SET_ADAPTER(TBT_ADAPTER_LEGACY);
 
 	/* Cable Discover Mode VDO */
 	data.cable_mode = TBT_MODE;
diff --git a/include/linux/usb/typec_tbt.h b/include/linux/usb/typec_tbt.h
index 55dcea12082c80defeb6f199ad333279b58adcd7..6bf208c9dd5037f162678bc0be5be7ae1ca0deca 100644
--- a/include/linux/usb/typec_tbt.h
+++ b/include/linux/usb/typec_tbt.h
@@ -27,8 +27,8 @@ struct typec_thunderbolt_data {
 /* TBT3 Device Discover Mode VDO bits */
 #define TBT_MODE			BIT(0)
 #define TBT_ADAPTER(_vdo_)		FIELD_GET(BIT(16), _vdo_)
-#define   TBT_ADAPTER_LEGACY		0
-#define   TBT_ADAPTER_TBT3		1
+#define   TBT_ADAPTER_TBT3		0
+#define   TBT_ADAPTER_LEGACY		1
 #define TBT_INTEL_SPECIFIC_B0		BIT(26)
 #define TBT_VENDOR_SPECIFIC_B0		BIT(30)
 #define TBT_VENDOR_SPECIFIC_B1		BIT(31)

---
base-commit: 8e2755d7779a95dd61d8997ebce33ff8b1efd3fb
change-id: 20250926-topic-tbt_header_bit_fix-17aeb524df4a

Best regards,
-- 
Konrad Dybcio <konrad.dybcio@....qualcomm.com>