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

Andrei Kuchynski
2025-09-05T14:22:22Z

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>
---
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