linux-kernel - Re: [PATCH v1 1/5] usb: typec: Add alt_mode

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Message-ID: <CAMMMRMeqAToQ=iAjLrT64q3g+e_K_3Mqp4uh3LNnULMTJeY-iw@mail.gmail.com>
Date: Thu, 21 Aug 2025 16:19:56 +0200
From: Andrei Kuchynski <akuchynski@...omium.org>
To: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>, Benson Leung <bleung@...omium.org>, 
	Jameson Thies <jthies@...gle.com>, Tzung-Bi Shih <tzungbi@...nel.org>, linux-usb@...r.kernel.org, 
	chrome-platform@...ts.linux.dev, Guenter Roeck <groeck@...omium.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, "Christian A. Ehrhardt" <lk@...e.de>, 
	Venkat Jayaraman <venkat.jayaraman@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/5] usb: typec: Add alt_mode_override field to port property

On Wed, Aug 20, 2025 at 12:53 PM Heikki Krogerus
<heikki.krogerus@...ux.intel.com> wrote:
>
> On Thu, Aug 14, 2025 at 06:44:51PM +0000, Andrei Kuchynski wrote:
> > This new field in the port properties dictates whether the Platform Policy
> > Manager (PPM) allows the OS Policy Manager (OPM) to change the currently
> > active, negotiated alternate mode.
> >
> > Signed-off-by: Andrei Kuchynski <akuchynski@...omium.org>
> > ---
> >  drivers/usb/typec/class.c | 14 +++++++++++---
> >  drivers/usb/typec/class.h |  2 ++
> >  include/linux/usb/typec.h |  1 +
> >  3 files changed, 14 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
> > index 67a533e35150..a72325ff099a 100644
> > --- a/drivers/usb/typec/class.c
> > +++ b/drivers/usb/typec/class.c
> > @@ -459,9 +459,16 @@ static umode_t typec_altmode_attr_is_visible(struct kobject *kobj,
> >       struct typec_altmode *adev = to_typec_altmode(kobj_to_dev(kobj));
> >
> >       if (attr == &dev_attr_active.attr)
> > -             if (!is_typec_port(adev->dev.parent) &&
> > -                 (!adev->ops || !adev->ops->activate))
> > -                     return 0444;
> > +             if (!is_typec_port(adev->dev.parent)) {
> > +                     struct typec_partner *partner =
> > +                             to_typec_partner(adev->dev.parent);
>
> That looks a bit unnecessary. Also, can't the altmode be a plug alt mode?
>
> > +                     struct typec_port *port =
> > +                             to_typec_port(partner->dev.parent);
> > +
> > +                     if (!port->alt_mode_override || !adev->ops ||
> > +                             !adev->ops->activate)
> > +                             return 0444;
> > +             }
>
> How about:
>
>         struct typec_altmode *adev = to_typec_altmode(kobj_to_dev(kobj));
>         struct typec_port *port = typec_altmode2port(adev);
>
>         if (attr == &dev_attr_active.attr) {
>                if (!is_typec_port(adev->dev.parent)) {
>                         if (!port->alt_mode_override || !adev->ops || !adev->ops->activate)
>                                 return 0444;
>                 }
>         }
>

I completely missed typec_altmode2port function.
Thank you!

> >       return attr->mode;
> >  }
> > @@ -2681,6 +2688,7 @@ struct typec_port *typec_register_port(struct device *parent,
> >       }
> >
> >       port->pd = cap->pd;
> > +     port->alt_mode_override = cap->alt_mode_override;
>
> This needs to be enabled by default:
>
>         port->alt_mode_override = !cap->no_mode_control;
>

Agreed.  I'll make it enabled by default.

> >       ret = device_add(&port->dev);
> >       if (ret) {
> > diff --git a/drivers/usb/typec/class.h b/drivers/usb/typec/class.h
> > index db2fe96c48ff..f05d9201c233 100644
> > --- a/drivers/usb/typec/class.h
> > +++ b/drivers/usb/typec/class.h
> > @@ -80,6 +80,8 @@ struct typec_port {
> >        */
> >       struct device                   *usb2_dev;
> >       struct device                   *usb3_dev;
> > +
> > +     bool                            alt_mode_override;
>
> s/alt_mode_override/mode_control/ ?
>

Agreed. mode_control is a clearer name.

Thank you for your review!


Andrei