usb: typec: ucsi: Detect and skip duplicate altmodes from buggy firmware

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 <stable@kernel.org>
Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao@canonical.com>
unchanged: still SVID+VDO exact-dup match.
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://patch.msgid.link/20260713084323.287516-1-acelan.kao@canonical.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index f56897e23df80402fbd158f16758bfb5026939c7..0db43521af3fd7e4952812ed2448527f3560e8fa 100644 (file)
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -529,6 +529,129 @@ err:
        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 but please contact the BIOS vendor to fix this issue.\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;