On Fri, Sep 5, 2025 at 12:25 PM Heikki Krogerus
[off-list ref] wrote:

On Mon, Aug 25, 2025 at 02:57:49PM +0000, Andrei Kuchynski wrote:

quoted

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;

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.

quoted

+             }
+     }
+
+     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