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>

0 files changed, 0 insertions, 0 deletions