Re: [PATCH v3 4/5] usb: typec: Implement alternate mode priority handling

Heikki Krogerus
2025-09-09T08:50:40Z

On Fri, Sep 05, 2025 at 02:22:05PM +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@chromium.org>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
> 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;
> + }
> + }
> +
> + 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);
> +}
> diff --git a/drivers/usb/typec/mode_selection.h b/drivers/usb/typec/mode_selection.h
> new file mode 100644
> index 000000000000..cbf5a37e6404
> --- /dev/null
> +++ b/drivers/usb/typec/mode_selection.h
> @@ -0,0 +1,6 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#include <linux/usb/typec_altmode.h>
> +
> +void typec_mode_set_priority(struct typec_altmode *alt,
> + const unsigned int priority);
> diff --git a/include/linux/usb/typec_altmode.h b/include/linux/usb/typec_altmode.h
> index b3c0866ea70f..571c6e00b54f 100644
> --- a/include/linux/usb/typec_altmode.h
> +++ b/include/linux/usb/typec_altmode.h
> @@ -28,6 +28,7 @@ struct typec_altmode {
> int mode;
> u32 vdo;
> unsigned int active:1;
> + unsigned int priority;
>
> char *desc;
> const struct typec_altmode_ops *ops;
> --
> 2.51.0.355.g5224444f11-goog

--
heikki