Re: [PATCH] usb: typec: ucsi: Skip CAM query when partner has no alt modes

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

On Mon, Sep 28, 2026 at 08:47:40AM +0000, Andrei Kuchynski wrote:
> On Sun, Sep 27, 2026 at 2:17 AM Gris Ge <cnfourt@gmail.com> wrote:
> >
> > Since Thunderbolt alternate mode support was added,
> > `ucsi_altmode_update_active()` is called on every Connector Partner
> > Changed event.  This made the driver send `UCSI_GET_CURRENT_CAM` to
> > PPMs even when the partner had no alternate modes registered. Firmware
> > that does not support the optional alternate mode details answered Not
> > Supported, which produced a spurious error on every partner change:
> >
> > ```
> > ucsi_acpi USBC000:00: GET_CURRENT_CAM command failed
> > ```
> >
> > Fixed by skipping the command when there is nothing to update.
> >
> > Fixes: da87d45b1951 ("usb: typec: ucsi: Add Thunderbolt alternate mode support")
> > Cc: stable@vger.kernel.org # v7.0+
> > Assisted-by: Codex:deepseek-v4.1-flash
> > Signed-off-by: Gris Ge <cnfourt@gmail.com>
> > ---
> >  drivers/usb/typec/ucsi/ucsi.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> > index bef3f9b71d71..71b28e4df470 100644
> > --- a/drivers/usb/typec/ucsi/ucsi.c
> > +++ b/drivers/usb/typec/ucsi/ucsi.c
> > @@ -360,6 +360,15 @@ void ucsi_altmode_update_active(struct ucsi_connector *con)
> >         u8 cur;
> >         int i;
> >
> > +       /*
> > +        * Alternate mode support is optional, and the PPM is not required to
> > +        * support GET_CURRENT_CAM when it does not support alternate modes.
> > +        * There is also nothing to update when the partner has not registered
> > +        * any alternate modes, so don't send the command in that case.
> > +        */
> > +       if (!con->partner_altmode[0])
> 
> Should we move this validation into ucsi_handle_connector_change?
> 
>         if (con->partner_altmode[0])
>                 ucsi_altmode_update_active(con);
> 
> All other call sites are already guarded by this condition.

Makes sense to me.

> Besides, I don't think we need that comment above.

I agree.

-- 
heikki