On Fri, Sep 5, 2025 at 12:25 PM Heikki Krogerus
<heikki.krogerus@xxxxxxxxxxxxxxx> wrote:
>
> On Mon, Aug 25, 2025 at 02:57:49PM +0000, Andrei Kuchynski wrote:
> > This patch introduces APIs to manage the priority of USB Type-C alternate
> > modes. These APIs allow for setting and retrieving a priority number for
> > each mode. If a new priority value conflicts with an existing mode's
> > priority, the priorities of the conflicting mode and all subsequent modes
> > are automatically incremented to ensure uniqueness.
> >
> > Signed-off-by: Andrei Kuchynski <akuchynski@xxxxxxxxxxxx>
> > ---
> > drivers/usb/typec/Makefile | 2 +-
> > drivers/usb/typec/mode_selection.c | 38 ++++++++++++++++++++++++++++++
> > drivers/usb/typec/mode_selection.h | 6 +++++
> > include/linux/usb/typec_altmode.h | 1 +
> > 4 files changed, 46 insertions(+), 1 deletion(-)
> > create mode 100644 drivers/usb/typec/mode_selection.c
> > create mode 100644 drivers/usb/typec/mode_selection.h
> >
> > diff --git a/drivers/usb/typec/Makefile b/drivers/usb/typec/Makefile
> > index 7a368fea61bc..8a6a1c663eb6 100644
> > --- a/drivers/usb/typec/Makefile
> > +++ b/drivers/usb/typec/Makefile
> > @@ -1,6 +1,6 @@
> > # SPDX-License-Identifier: GPL-2.0
> > obj-$(CONFIG_TYPEC) += typec.o
> > -typec-y := class.o mux.o bus.o pd.o retimer.o
> > +typec-y := class.o mux.o bus.o pd.o retimer.o mode_selection.o
> > typec-$(CONFIG_ACPI) += port-mapper.o
> > obj-$(CONFIG_TYPEC) += altmodes/
> > obj-$(CONFIG_TYPEC_TCPM) += tcpm/
> > diff --git a/drivers/usb/typec/mode_selection.c b/drivers/usb/typec/mode_selection.c
> > new file mode 100644
> > index 000000000000..2179bf25f5d4
> > --- /dev/null
> > +++ b/drivers/usb/typec/mode_selection.c
> > @@ -0,0 +1,38 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Copyright 2025 Google LLC.
> > + */
> > +
> > +#include "mode_selection.h"
> > +#include "class.h"
> > +#include "bus.h"
> > +
> > +static int increment_duplicated_priority(struct device *dev, void *data)
> > +{
> > + struct typec_altmode **alt_target = (struct typec_altmode **)data;
> > +
> > + if (is_typec_altmode(dev)) {
> > + struct typec_altmode *alt = to_typec_altmode(dev);
> > +
> > + if (alt != *alt_target && alt->priority == (*alt_target)->priority) {
> > + alt->priority++;
> > + *alt_target = alt;
> > + return 1;
>
> Couldn't you just always return 0?
>
Priority values for each mode are consistently unique, eliminating the need
for further processing if a duplicate is found.
> > + }
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +void typec_mode_set_priority(struct typec_altmode *alt,
> > + const unsigned int priority)
> > +{
> > + struct typec_port *port = to_typec_port(alt->dev.parent);
> > + int res = 1;
> > +
> > + alt->priority = priority;
> > +
> > + while (res)
> > + res = device_for_each_child(&port->dev, &alt,
> > + increment_duplicated_priority);
>
> Then this could be:
>
> device_for_each_child(&port->dev, &alt, increment_duplicated_priority);
>
> right?
>
Unfortunately, the child's list is not in prioritized order. When a
duplicated value is found, the cycle should start for the whole list again.
I definitely need a loop here.
Thanks,
Andrei
