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

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

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.

> +				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;
        ...

> +
> +	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