Re: [PATCH v2 1/3] usb: typec: ucsi: Detect and skip duplicate altmodes from buggy firmware

Chia-Lin Kao (AceLan)
2025-12-04T03:08:38Z

On Mon, Nov 17, 2025 at 11:00:29AM +0200, Heikki Krogerus wrote:
> Hi,
>
> Tue, Nov 11, 2025 at 09:05:39AM +0800, Chia-Lin Kao (AceLan) kirjoitti:
> > 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>
> > ---
> > drivers/usb/typec/ucsi/ucsi.c | 77 +++++++++++++++++++++++++++++++++++
> > 1 file changed, 77 insertions(+)
> >
> > diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> > index 3f568f790f39..7b79e7491094 100644
> > --- a/drivers/usb/typec/ucsi/ucsi.c
> > +++ b/drivers/usb/typec/ucsi/ucsi.c
> > @@ -556,6 +556,74 @@ ucsi_register_altmodes_nvidia(struct ucsi_connector *con, u8 recipient)
> > return 0;
> > }
> >
> > +/*
> > + * 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)
> > +{
> > + 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 */
> > + if (recipient == UCSI_RECIPIENT_SOP) {
> > + for (k = 0; k < UCSI_MAX_ALTMODES; k++) {
> > + if (!con->partner_altmode[k])
> > + break;
> > + /*
> > + * Some buggy firmware returns the same SVID multiple times
> > + * with different VDOs. This causes duplicate device registration
> > + * and sysfs errors. Check SVID only for partner altmodes.
> > + */
> > + if (con->partner_altmode[k]->svid == svid) {
>
> I'm not sure this works. Some vendor specific modes always come in
> pairs. Check Apple for example. I think you always need to check the
> VID on top of the SVID.
Sorry, just found that my emails were queued/deferred locally.

What does VID means here? USB VID?
I'm not quite understanding what you're trying to do.
Could you elaborate?

>
> > + dev_warn(con->ucsi->dev,
> > + "con%d: Firmware bug: duplicate partner altmode SVID 0x%04x (VDO 0x%08x vs 0x%08x) at offset %d, ignoring. Please update your system firmware.\n",
> > + con->num, svid, con->partner_altmode[k]->vdo,
> > + vdo, offset);
> > + return true;
> > + }
> > + }
> > + } else if (recipient == UCSI_RECIPIENT_CON) {
> > + for (k = 0; k < UCSI_MAX_ALTMODES; k++) {
> > + if (!con->port_altmode[k])
> > + break;
> > + if (con->port_altmode[k]->svid == svid &&
> > + con->port_altmode[k]->vdo == vdo) {
> > + dev_warn_once(con->ucsi->dev,
> > + "con%d: Firmware bug: duplicate port altmode SVID 0x%04x at offset %d, ignoring. Please update your system firmware.\n",
> > + con->num, svid, offset);
> > + return true;
> > + }
> > + }
> > + } else if (recipient == UCSI_RECIPIENT_SOP_P) {
> > + for (k = 0; k < UCSI_MAX_ALTMODES; k++) {
> > + if (!con->plug_altmode[k])
> > + break;
> > + if (con->plug_altmode[k]->svid == svid &&
> > + con->plug_altmode[k]->vdo == vdo) {
> > + dev_warn_once(con->ucsi->dev,
> > + "con%d: Firmware bug: duplicate plug altmode SVID 0x%04x at offset %d, ignoring. Please update your system firmware.\n",
> > + con->num, svid, offset);
> > + return true;
> > + }
> > + }
> > + }
>
> struct typec_altmode *altmodes;
>
> switch (recipient) {
> case UCSI_RECIPIENT_CON:
> altmodes = con->port->altmode;
> break;
> case UCSI_RECIPIENT_SOP_P:
> altmodes = con->plug_altmode;
> break;
> ...
Cool, this make the code cleaner, I'll submit v3 later.

>
> > +
> > + return false;
> > +}
> > +
> > static int ucsi_register_altmodes(struct ucsi_connector *con, u8 recipient)
> > {
> > int max_altmodes = UCSI_MAX_ALTMODES;
> > @@ -605,6 +673,15 @@ 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;
> > --
> > 2.43.0
>
> thanks,
>
> --
> heikki