[PATCH v3 5/5] usb: typec: Expose alternate mode priority via sysfs

Andrei Kuchynski
2025-09-05T14:22:25Z

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@chromium.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
---
Documentation/ABI/testing/sysfs-class-typec | 11 +++++++
drivers/usb/typec/class.c | 32 ++++++++++++++++++++-
2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-class-typec b/Documentation/ABI/testing/sysfs-class-typec
index 38e101c17a00..dab3e4e727b6 100644
--- a/Documentation/ABI/testing/sysfs-class-typec
+++ b/Documentation/ABI/testing/sysfs-class-typec
@@ -162,6 +162,17 @@ 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@chromium.org>
+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.
+
USB Type-C partner devices (eg. /sys/class/typec/port0-partner/)

What: /sys/class/typec/<port>-partner/accessory_mode
diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
index 9f86605ce125..aaab2e1e98b4 100644
--- a/drivers/usb/typec/class.c
+++ b/drivers/usb/typec/class.c
@@ -19,6 +19,7 @@
#include "bus.h"
#include "class.h"
#include "pd.h"
+#include "mode_selection.h"

static DEFINE_IDA(typec_index_ida);

@@ -445,11 +446,34 @@ svid_show(struct device *dev, struct device_attribute *attr, char *buf)
}
static DEVICE_ATTR_RO(svid);

+static ssize_t priority_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t size)
+{
+ unsigned int val;
+ int err = kstrtouint(buf, 10, &val);
+
+ if (!err) {
+ typec_mode_set_priority(to_typec_altmode(dev), val);
+ return size;
+ }
+
+ return err;
+}
+
+static ssize_t priority_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%u\n", to_typec_altmode(dev)->priority);
+}
+static DEVICE_ATTR_RW(priority);
+
static struct attribute *typec_altmode_attrs[] = {
&dev_attr_active.attr,
&dev_attr_mode.attr,
&dev_attr_svid.attr,
&dev_attr_vdo.attr,
+ &dev_attr_priority.attr,
NULL
};

@@ -459,11 +483,15 @@ static umode_t typec_altmode_attr_is_visible(struct kobject *kobj,
struct typec_altmode *adev = to_typec_altmode(kobj_to_dev(kobj));
struct typec_port *port = typec_altmode2port(adev);

- if (attr == &dev_attr_active.attr)
+ if (attr == &dev_attr_active.attr) {
if (!is_typec_port(adev->dev.parent)) {
if (!port->mode_control || !adev->ops || !adev->ops->activate)
return 0444;
}
+ } else if (attr == &dev_attr_priority.attr) {
+ if (!is_typec_port(adev->dev.parent) || !port->mode_control)
+ return 0;
+ }

return attr->mode;
}
@@ -2491,6 +2519,8 @@ typec_port_register_altmode(struct typec_port *port,
to_altmode(adev)->retimer = retimer;
}

+ typec_mode_set_priority(adev, 0);
+
return adev;
}
EXPORT_SYMBOL_GPL(typec_port_register_altmode);
--
2.51.0.355.g5224444f11-goog