linux-kernel - [PATCH v1 5/5] usb: typec: Expose alternate mode priority via sysfs

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Message-ID: <20250814184455.723170-6-akuchynski@chromium.org>
Date: Thu, 14 Aug 2025 18:44:55 +0000
From: Andrei Kuchynski <akuchynski@...omium.org>
To: Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
	Benson Leung <bleung@...omium.org>,
	Jameson Thies <jthies@...gle.com>,
	Tzung-Bi Shih <tzungbi@...nel.org>,
	linux-usb@...r.kernel.org,
	chrome-platform@...ts.linux.dev
Cc: Guenter Roeck <groeck@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
	"Christian A. Ehrhardt" <lk@...e.de>,
	Venkat Jayaraman <venkat.jayaraman@...el.com>,
	linux-kernel@...r.kernel.org,
	Andrei Kuchynski <akuchynski@...omium.org>
Subject: [PATCH v1 5/5] usb: typec: Expose alternate mode priority via sysfs

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@...omium.org>
---
 Documentation/ABI/testing/sysfs-class-typec | 12 ++++++
 drivers/usb/typec/class.c                   | 47 ++++++++++++++++++++-
 2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-class-typec b/Documentation/ABI/testing/sysfs-class-typec
index 38e101c17a00..001202d651fa 100644
--- a/Documentation/ABI/testing/sysfs-class-typec
+++ b/Documentation/ABI/testing/sysfs-class-typec
@@ -162,6 +162,18 @@ 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@...omium.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.
+		This attribute is visible only if the kernel supports mode selection.
+
 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 a72325ff099a..708f3487222a 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 +446,41 @@ 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) {
+		err = typec_mode_set_priority(to_typec_altmode(dev), val);
+		if (!err)
+			return size;
+	}
+
+	return err;
+}
+
+static ssize_t priority_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	int val;
+	const int err = typec_mode_get_priority(to_typec_altmode(dev), &val);
+
+	if (err)
+		return err;
+
+	return sprintf(buf, "%d\n", val);
+}
+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
 };
 
@@ -458,7 +489,7 @@ static umode_t typec_altmode_attr_is_visible(struct kobject *kobj,
 {
 	struct typec_altmode *adev = to_typec_altmode(kobj_to_dev(kobj));
 
-	if (attr == &dev_attr_active.attr)
+	if (attr == &dev_attr_active.attr) {
 		if (!is_typec_port(adev->dev.parent)) {
 			struct typec_partner *partner =
 				to_typec_partner(adev->dev.parent);
@@ -469,6 +500,15 @@ static umode_t typec_altmode_attr_is_visible(struct kobject *kobj,
 				!adev->ops->activate)
 				return 0444;
 		}
+	} else if (attr == &dev_attr_priority.attr) {
+		if (is_typec_port(adev->dev.parent))  {
+			struct typec_port *port = to_typec_port(adev->dev.parent);
+
+			if (!port->alt_mode_override)
+				return 0;
+		} else
+			return 0;
+	}
 
 	return attr->mode;
 }
@@ -2029,6 +2069,7 @@ static void typec_release(struct device *dev)
 	typec_mux_put(port->mux);
 	typec_retimer_put(port->retimer);
 	kfree(port->cap);
+	typec_mode_selection_destroy(port);
 	kfree(port);
 }
 
@@ -2496,6 +2537,8 @@ typec_port_register_altmode(struct typec_port *port,
 		to_altmode(adev)->retimer = retimer;
 	}
 
+	typec_mode_set_priority(adev, -1);
+
 	return adev;
 }
 EXPORT_SYMBOL_GPL(typec_port_register_altmode);
@@ -2645,6 +2688,8 @@ struct typec_port *typec_register_port(struct device *parent,
 	port->con.attach = typec_partner_attach;
 	port->con.deattach = typec_partner_deattach;
 
+	INIT_LIST_HEAD(&port->mode_list);
+
 	if (cap->usb_capability & USB_CAPABILITY_USB4)
 		port->usb_mode = USB_MODE_USB4;
 	else if (cap->usb_capability & USB_CAPABILITY_USB3)
-- 
2.51.0.rc0.215.g125493bb4a-goog