[PATCH v4 1/3] usb: typec: ucsi: Detect and skip duplicate altmodes from buggy firmware

Chia-Lin Kao (AceLan)
2026-04-13T07:36:06Z

Some firmware implementations incorrectly return the same altmode
multiple times at different offsets when queried via UCSI_GET_ALTERNATE_MODES.
This causes sysfs duplicate filename errors and kernel call traces when
the driver attempts to register the same altmode twice:

sysfs: cannot create duplicate filename '/devices/.../typec/port0/port0.0/partner'
typec-thunderbolt port0-partner.1: failed to create symlinks
typec-thunderbolt port0-partner.1: probe with driver typec-thunderbolt failed with error -17

Detect duplicate altmodes by comparing SVID and VDO before registration.
If a duplicate is detected, skip it and print a single clean warning
message instead of generating a kernel call trace:

ucsi_acpi USBC000:00: con2: Firmware bug: duplicate partner altmode SVID 0x8087 (VDO 0x8087a043 vs 0x00000001) at offset 1, ignoring. Please update your system firmware.

This makes the error handling more user-friendly while still alerting
users to the firmware bug.

The duplicate detection logic is implemented in a reusable helper
function ucsi_altmode_is_duplicate() and used in ucsi_register_altmodes().
The fix applies to all three recipient types: partner (SOP), port (CON),
and plug (SOP_P) altmodes.

Fixes: a79f16efcd00 ("usb: typec: ucsi: Add support for the partner USB Modes")
Cc: stable@vger.kernel.org
Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao@canonical.com>
---
v4. rebase
v3. 1. move ucsi_altmode_is_duplicate() before ucsi_register_altmodes_nvidia()
for later modification on ucsi_register_altmodes_nvidia()
2. use struct typec_altmode **altmodes to simplify the logic
---
drivers/usb/typec/ucsi/ucsi.c | 76 +++++++++++++++++++++++++++++++++++
1 file changed, 76 insertions(+)

diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index f181afca2bb28..eebbb80fae566 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -498,6 +498,73 @@ static int ucsi_register_altmode(struct ucsi_connector *con,
return ret;
}

+/*
+ * Check if an altmode is a duplicate. Some firmware implementations
+ * incorrectly return the same altmode multiple times, causing sysfs errors.
+ * Returns true if the altmode should be skipped.
+ */
+static bool ucsi_altmode_is_duplicate(struct ucsi_connector *con, u8 recipient,
+ const struct ucsi_altmode *alt_batch, int batch_idx,
+ u16 svid, u32 vdo, int offset)
+{
+ struct typec_altmode **altmodes;
+ const char *recipient_name;
+ int k;
+
+ /* Check for duplicates within the current batch first */
+ for (k = 0; k < batch_idx; k++) {
+ if (alt_batch[k].svid == svid && alt_batch[k].mid == vdo) {
+ dev_warn_once(con->ucsi->dev,
+ "con%d: Firmware bug: duplicate altmode SVID 0x%04x in same response at offset %d, ignoring. Please update your system firmware.\n",
+ con->num, svid, offset);
+ return true;
+ }
+ }
+
+ /* Check for duplicates in already registered altmodes */
+
+ switch (recipient) {
+ case UCSI_RECIPIENT_CON:
+ altmodes = con->port_altmode;
+ recipient_name = "port";
+ break;
+ case UCSI_RECIPIENT_SOP:
+ altmodes = con->partner_altmode;
+ recipient_name = "partner";
+ break;
+ case UCSI_RECIPIENT_SOP_P:
+ altmodes = con->plug_altmode;
+ recipient_name = "plug";
+ break;
+ default:
+ return false;
+ }
+
+ for (k = 0; k < UCSI_MAX_ALTMODES; k++) {
+ if (!altmodes[k])
+ break;
+
+ /* Check SVID for all, VDO only for non-SOP */
+ if (altmodes[k]->svid != svid)
+ continue;
+ if (recipient != UCSI_RECIPIENT_SOP && altmodes[k]->vdo != vdo)
+ continue;
+
+ if (recipient == UCSI_RECIPIENT_SOP) {
+ dev_warn(con->ucsi->dev,
+ "con%d: Firmware bug: duplicate %s altmode SVID 0x%04x (VDO 0x%08x vs 0x%08x) at offset %d, ignoring. Please update your system firmware.\n",
+ con->num, recipient_name, svid, altmodes[k]->vdo, vdo, offset);
+ } else {
+ dev_warn_once(con->ucsi->dev,
+ "con%d: Firmware bug: duplicate %s altmode SVID 0x%04x at offset %d, ignoring. Please update your system firmware.\n",
+ con->num, recipient_name, svid, offset);
+ }
+ return true;
+ }
+
+ return false;
+}
+
static int
ucsi_register_altmodes_nvidia(struct ucsi_connector *con, u8 recipient)
{
@@ -622,6 +689,15 @@ static int ucsi_register_altmodes(struct ucsi_connector *con, u8 recipient)
if (!alt[j].svid)
return 0;

+ /*
+ * Check for duplicates in current batch and already
+ * registered altmodes. Skip if duplicate found.
+ */
+ if (ucsi_altmode_is_duplicate(con, recipient, alt, j,
+ alt[j].svid, alt[j].mid,
+ i - num + j))
+ continue;
+
memset(&desc, 0, sizeof(desc));
desc.vdo = alt[j].mid;
desc.svid = alt[j].svid;
--
2.53.0