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

[Heikki Krogerus]

Hi Chia-Lin,

Mon, Oct 20, 2025 at 12:36:51PM +0300, Dmitry Baryshkov kirjoitti:
> On Mon, Oct 20, 2025 at 12:18:31PM +0300, Heikki Krogerus wrote:
> > +Antony
> > 
> > On Thu, Oct 16, 2025 at 01:53:32PM +0800, Chia-Lin Kao (AceLan) wrote:
> > > 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: con0: Firmware bug: duplicate partner altmode SVID 0x8087 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 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@xxxxxxxxxxxxxxx
> > > Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao@xxxxxxxxxxxxx>
> > 
> > Thank you for the patch. Before going forward with this, I would like
> > to make sure that Dell is not using the GET_ALTERNATE_MODES command in
> > some customised way deliberately, and that this really is a bug in the
> > EC firmware.
> 
> 
> Just to point out, we have had a similar issue with Lenovo Yoga c630,
> see yoga_c630_ucsi_update_altmodes(), the EC was ignoring offset field.

I think we can reuse that function like Dmitry pointed out. Can you
check that?

thanks,

-- 
heikki