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

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Message-ID: <66gkc32hdbzdxpnx3r56bfzt4znw6xj7m3j6363mus4nf47kf6@3f2hj5qwsb46>
Date: Mon, 20 Oct 2025 12:36:51 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc: "Chia-Lin Kao (AceLan)" <acelan.kao@...onical.com>,
        "Chen, Antony" <antony.chen@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Fedor Pchelkin <boddah8794@...il.com>,
        Andrei Kuchynski <akuchynski@...omium.org>,
        Venkat Jayaraman <venkat.jayaraman@...el.com>,
        Myrrh Periwinkle <myrrhperiwinkle@...labs.xyz>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: typec: ucsi: Detect and skip duplicate altmodes
 from buggy firmware

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@...r.kernel.org
> > Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao@...onical.com>
> 
> 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.

> 
> After seeing the trace output when this happens, it looked to me as
> the first response to the GET_ALTERNATE_MODES fills the MID field in
> the response data structure with different SVIDs for some reason
> (maybe with all supported SVIDs)? If that's deliberate it means we
> should drop the first response, and start registering from the second
> one.
> 
> If I've understood correctly, we have people contacting Dell about
> this.
> 
> thanks,
> 
> -- 
> heikki

-- 
With best wishes
Dmitry