On Thu, Aug 21, 2025 at 9:36 AM Heikki Krogerus
<heikki.krogerus@xxxxxxxxxxxxxxx> wrote:
>
> Hi Andrei,
>
> On Thu, Aug 14, 2025 at 06:44:55PM +0000, Andrei Kuchynski wrote:
> > This patch introduces a priority sysfs attribute to the USB Type-C
> > alternate mode port interface. This new attribute allows user-space to
> > configure the numeric priority of alternate modes managing their preferred
> > order of operation.
> >
> > Signed-off-by: Andrei Kuchynski <akuchynski@xxxxxxxxxxxx>
> > ---
> > Documentation/ABI/testing/sysfs-class-typec | 12 ++++++
> > drivers/usb/typec/class.c | 47 ++++++++++++++++++++-
> > 2 files changed, 58 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/ABI/testing/sysfs-class-typec b/Documentation/ABI/testing/sysfs-class-typec
> > index 38e101c17a00..001202d651fa 100644
> > --- a/Documentation/ABI/testing/sysfs-class-typec
> > +++ b/Documentation/ABI/testing/sysfs-class-typec
> > @@ -162,6 +162,18 @@ Description: Lists the supported USB Modes. The default USB mode that is used
> > - usb3 (USB 3.2)
> > - usb4 (USB4)
> >
> > + What: /sys/class/typec/<port>/<alt-mode>/priority
> > +Date: July 2025
> > +Contact: Andrei Kuchynski <akuchynski@xxxxxxxxxxxx>
> > +Description:
> > + Displays and allows setting the priority for a specific alt-mode.
> > + When read, it shows the current integer priority value. Lower numerical
> > + values indicate higher priority (0 is the highest priority).
> > + If the new value is already in use by another mode, the priority of the
> > + conflicting mode and any subsequent modes will be incremented until they
> > + are all unique.
> > + This attribute is visible only if the kernel supports mode selection.
>
> I was expecting this to be already used in this series.
>
> IMO this file should be the only thing the user space needs to use by
> default at least.
>
No more entries for mode priorities.
What about the trigger of the process?
I'm going to introduce a mode_selection binary sysfs attribute in
the next series. Writing 1 to this attribute will activate the
mode selection process. Writing 0 will cancel the process and
exit the currently active mode.
> > @@ -469,6 +500,15 @@ static umode_t typec_altmode_attr_is_visible(struct kobject *kobj,
> > !adev->ops->activate)
> > return 0444;
> > }
> > + } else if (attr == &dev_attr_priority.attr) {
> > + if (is_typec_port(adev->dev.parent)) {
> > + struct typec_port *port = to_typec_port(adev->dev.parent);
> > +
> > + if (!port->alt_mode_override)
> > + return 0;
> > + } else
> > + return 0;
> > + }
>
> If we have the local port variable, this should be enough:
>
> if (!is_typec_port(adev->dev.parent) || !port->alt_mode_override)
> return 0;
>
typec_altmode2port is really powerful. Thank you again for this hint!
> > return attr->mode;
> > }
> > @@ -2029,6 +2069,7 @@ static void typec_release(struct device *dev)
> > typec_mux_put(port->mux);
> > typec_retimer_put(port->retimer);
> > kfree(port->cap);
> > + typec_mode_selection_destroy(port);
> > kfree(port);
> > }
> >
> > @@ -2496,6 +2537,8 @@ typec_port_register_altmode(struct typec_port *port,
> > to_altmode(adev)->retimer = retimer;
> > }
> >
> > + typec_mode_set_priority(adev, -1);
>
> This really should not be necessary. Why can't we set the priority
> based on the order the drives registers the altmodes for the port?
>
Setting priorities based on the order of registration is a good
idea. This simplifies the logic by making the default_priorities
unnecessary.
I will modify the initialization to call
typec_mode_set_priority(adev, 0);
With this change, the later a mode is registered, the higher its
priority will be. For the cros_ec_typec driver, this produces the
same default sequence: USB4 TBT DP.
Thanks,
Andrei
> > return adev;
> > }
> > EXPORT_SYMBOL_GPL(typec_port_register_altmode);
> > @@ -2645,6 +2688,8 @@ struct typec_port *typec_register_port(struct device *parent,
> > port->con.attach = typec_partner_attach;
> > port->con.deattach = typec_partner_deattach;
> >
> > + INIT_LIST_HEAD(&port->mode_list);
> > +
> > if (cap->usb_capability & USB_CAPABILITY_USB4)
> > port->usb_mode = USB_MODE_USB4;
> > else if (cap->usb_capability & USB_CAPABILITY_USB3)
>
> thanks,
>
> --
> heikki
