[PATCH v6 1/3] usb: typec: ucsi: Detect and skip duplicate altmodes from buggy firmware
From: Chia-Lin Kao (AceLan)
Date: Fri Jun 12 2026 - 01:28:52 EST
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
The matching rules differ by recipient:
- UCSI_RECIPIENT_CON (port) and UCSI_RECIPIENT_SOP_P (plug):
Two altmodes with identical SVID and VDO are byte-for-byte
duplicates and the second has no observable function, so drop it.
- UCSI_RECIPIENT_SOP (partner):
The typec class binds each partner altmode to a port altmode of
the same SVID via altmode_match()/device_find_child(), which
returns the first port altmode with a matching SVID. If the
partner advertises more altmodes for SVID X than the port
advertises, the surplus partner altmode(s) collapse onto an
already-paired port altmode and trigger the
"duplicate filename .../partner" sysfs error during
typec_altmode_create_links(). Use the port-side altmode count for
SVID X as the authoritative cap and reject any partner altmode
that would exceed it. This preserves legitimate multi-Mode
partner altmodes (vendor SVIDs that the port really does
advertise more than once) while filtering the firmware-generated
duplicates that have no port counterpart, and is therefore
stricter than a plain SVID+VDO comparison (which still admits the
Thunderbolt case where firmware reports the same SVID twice with
different VDOs) without being over-broad like a plain SVID match
(which would falsely drop legitimate vendor multi-Mode entries).
If a duplicate is detected, skip it and emit a clean warning instead
of generating a kernel call trace:
ucsi_acpi USBC000:00: con2: Firmware bug: duplicate partner altmode SVID 0x8087 at offset 1, ignoring.
ucsi_acpi USBC000:00: con2: VDO mismatch: 0x8087a043 vs 0x00000001
The duplicate detection logic lives in a reusable helper
ucsi_altmode_is_duplicate() and is invoked from
ucsi_register_altmodes(). It 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@xxxxxxxxxxxxxxx
Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao@xxxxxxxxxxxxx>
--
v6. - New helper ucsi_altmode_count_svid() counts altmodes with a given
SVID in any of the per-connector altmode arrays.
- ucsi_altmode_is_duplicate() for UCSI_RECIPIENT_SOP no longer asks
"have I seen this SVID before". It now checks whether
partner_count_for(svid) >= port_count_for(svid) and rejects only the
surplus.
- For UCSI_RECIPIENT_CON and UCSI_RECIPIENT_SOP_P, behavior is
unchanged: still SVID+VDO exact-dup match.
- Commit message rewritten to spell out the per-recipient rules and
why partner needs the cardinality cap (avoids both the SVID-only
false positives that hurt the legitimate Dell 0x413c case and the
SVID+VDO false negatives that let the Thunderbolt 0x8087 firmware
bug through).
---
drivers/usb/typec/ucsi/ucsi.c | 132 ++++++++++++++++++++++++++++++++++
1 file changed, 132 insertions(+)
diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index 92166a3725b16..9cd7fd7a38521 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -529,6 +529,129 @@ static int ucsi_register_altmode(struct ucsi_connector *con,
return ret;
}
+static void ucsi_dump_duplicate_altmode(struct ucsi_connector *con,
+ u8 recipient, u16 svid,
+ u32 existing_vdo, u32 new_vdo,
+ int offset)
+{
+ static const char * const recipient_names[] = {
+ [UCSI_RECIPIENT_CON] = "port",
+ [UCSI_RECIPIENT_SOP] = "partner",
+ [UCSI_RECIPIENT_SOP_P] = "plug",
+ [UCSI_RECIPIENT_SOP_PP] = "cable plug prime",
+ };
+
+ dev_warn(con->ucsi->dev,
+ "con%d: Firmware bug: duplicate %s altmode SVID 0x%04x at offset %d, ignoring.\n",
+ con->num, recipient_names[recipient], svid, offset);
+
+ if (existing_vdo != new_vdo)
+ dev_warn(con->ucsi->dev,
+ "con%d: VDO mismatch: 0x%08x vs 0x%08x\n",
+ con->num, existing_vdo, new_vdo);
+}
+
+/* Count altmodes in @altmodes that advertise @svid. */
+static int ucsi_altmode_count_svid(struct typec_altmode **altmodes, u16 svid)
+{
+ int count = 0;
+ int k;
+
+ for (k = 0; k < UCSI_MAX_ALTMODES; k++) {
+ if (!altmodes[k])
+ break;
+ if (altmodes[k]->svid == svid)
+ count++;
+ }
+
+ return count;
+}
+
+/*
+ * 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.
+ *
+ * The matching rules differ by recipient:
+ *
+ * - UCSI_RECIPIENT_CON (port) and UCSI_RECIPIENT_SOP_P (plug):
+ * Two altmodes with identical SVID and VDO are byte-for-byte duplicates
+ * and the second has no observable function. Drop them.
+ *
+ * - UCSI_RECIPIENT_SOP (partner):
+ * The typec class binds each partner altmode to a port altmode of the
+ * same SVID via altmode_match()/device_find_child(), which returns the
+ * first port altmode with a matching SVID. If the partner advertises
+ * more altmodes for SVID X than the port advertises, the surplus
+ * partner altmode(s) collapse onto an already-paired port altmode and
+ * trigger a "duplicate filename .../partner" sysfs error during
+ * typec_altmode_create_links(). Use the port-side altmode count for
+ * SVID X as the authoritative cap and reject any partner altmode that
+ * would exceed it. This preserves legitimate multi-Mode partner
+ * altmodes (e.g. vendor SVIDs that the port really does advertise
+ * twice) while filtering the firmware-generated duplicates that have
+ * no port counterpart.
+ */
+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;
+ int port_count, partner_count;
+ 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) {
+ ucsi_dump_duplicate_altmode(con, recipient, svid,
+ vdo, vdo, offset);
+ return true;
+ }
+ }
+
+ switch (recipient) {
+ case UCSI_RECIPIENT_SOP:
+ /*
+ * Cap partner altmodes per SVID by the port-side count:
+ * any further partner altmode for that SVID would alias an
+ * already-paired port altmode and break typec sysfs.
+ */
+ port_count = ucsi_altmode_count_svid(con->port_altmode, svid);
+ partner_count = ucsi_altmode_count_svid(con->partner_altmode,
+ svid);
+ if (port_count && partner_count >= port_count) {
+ ucsi_dump_duplicate_altmode(con, recipient, svid,
+ con->partner_altmode[partner_count - 1]->vdo,
+ vdo, offset);
+ return true;
+ }
+ return false;
+ case UCSI_RECIPIENT_CON:
+ altmodes = con->port_altmode;
+ break;
+ case UCSI_RECIPIENT_SOP_P:
+ altmodes = con->plug_altmode;
+ break;
+ default:
+ return false;
+ }
+
+ /* CON and SOP_P: drop only exact SVID+VDO duplicates. */
+ for (k = 0; k < UCSI_MAX_ALTMODES; k++) {
+ if (!altmodes[k])
+ break;
+
+ if (altmodes[k]->svid != svid || altmodes[k]->vdo != vdo)
+ continue;
+
+ ucsi_dump_duplicate_altmode(con, recipient, svid,
+ altmodes[k]->vdo, vdo, offset);
+ return true;
+ }
+
+ return false;
+}
+
static int
ucsi_register_altmodes_nvidia(struct ucsi_connector *con, u8 recipient)
{
@@ -653,6 +776,15 @@ 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