usb: typec: Add attribute file showing the supported USB modes of the port

This attribute file, named "usb_capability", will show the
supported USB modes, which are USB 2.0, USB 3.2 and USB4.
These modes are defined in the USB Type-C (R2.0) and USB
Power Delivery (R3.0 V2.0) Specifications.

Signed-off-by: Heikki Krogerus <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/ABI/testing/sysfs-class-typec

···
 		advertise to the partner. The currently used capabilities are in
 		brackets. Selection happens by writing to the file.
 
+What:		/sys/class/typec/<port>/usb_capability
+Date:		November 2024
+Contact:	Heikki Krogerus <[e-mail]>
+Description:	Lists the supported USB Modes. The default USB mode that is used
+		next time with the Enter_USB Message is in brackets. The default
+		mode can be changed by writing to the file when supported by the
+		driver.
+
+		Valid values:
+		- usb2 (USB 2.0)
+		- usb3 (USB 3.2)
+		- usb4 (USB4)
+
 USB Type-C partner devices (eg. /sys/class/typec/port0-partner/)
 
 What:		/sys/class/typec/<port>-partner/accessory_mode

drivers/usb/typec/class.c

···
 						char *buf);
 static DEVICE_ATTR_RO(usb_power_delivery_revision);
 
+static const char * const usb_modes[] = {
+	[USB_MODE_NONE] = "none",
+	[USB_MODE_USB2] = "usb2",
+	[USB_MODE_USB3] = "usb3",
+	[USB_MODE_USB4] = "usb4"
+};
+
 /* ------------------------------------------------------------------------- */
 /* Alternate Modes */
 
···
 /* USB Type-C ports */
 
 /**
+ * typec_port_set_usb_mode - Set the operational USB mode for the port
+ * @port: USB Type-C port
+ * @mode: USB Mode (USB2, USB3 or USB4)
+ *
+ * @mode will be used with the next Enter_USB message. Existing connections are
+ * not affected.
+ */
+void typec_port_set_usb_mode(struct typec_port *port, enum usb_mode mode)
+{
+	port->usb_mode = mode;
+}
+EXPORT_SYMBOL_GPL(typec_port_set_usb_mode);
+
+static ssize_t
+usb_capability_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct typec_port *port = to_typec_port(dev);
+	int len = 0;
+	int i;
+
+	for (i = USB_MODE_USB2; i < USB_MODE_USB4 + 1; i++) {
+		if (!(BIT(i - 1) & port->cap->usb_capability))
+			continue;
+
+		if (i == port->usb_mode)
+			len += sysfs_emit_at(buf, len, "[%s] ", usb_modes[i]);
+		else
+			len += sysfs_emit_at(buf, len, "%s ", usb_modes[i]);
+	}
+
+	sysfs_emit_at(buf, len - 1, "\n");
+
+	return len;
+}
+
+static ssize_t
+usb_capability_store(struct device *dev, struct device_attribute *attr,
+		     const char *buf, size_t size)
+{
+	struct typec_port *port = to_typec_port(dev);
+	int ret = 0;
+	int mode;
+
+	if (!port->ops || !port->ops->default_usb_mode_set)
+		return -EOPNOTSUPP;
+
+	mode = sysfs_match_string(usb_modes, buf);
+	if (mode < 0)
+		return mode;
+
+	ret = port->ops->default_usb_mode_set(port, mode);
+	if (ret)
+		return ret;
+
+	port->usb_mode = mode;
+
+	return size;
+}
+static DEVICE_ATTR_RW(usb_capability);
+
+/**
  * typec_port_set_usb_power_delivery - Assign USB PD for port.
  * @port: USB Type-C port.
  * @pd: USB PD instance.
···
 	&dev_attr_vconn_source.attr,
 	&dev_attr_port_type.attr,
 	&dev_attr_orientation.attr,
+	&dev_attr_usb_capability.attr,
 	NULL,
 };
 
···
 		if (port->cap->orientation_aware)
 			return 0444;
 		return 0;
+	} else if (attr == &dev_attr_usb_capability.attr) {
+		if (!port->cap->usb_capability)
+			return 0;
+		if (!port->ops || !port->ops->default_usb_mode_set)
+			return 0444;
 	}
 
 	return attr->mode;
···
 	port->prefer_role = cap->prefer_role;
 	port->con.attach = typec_partner_attach;
 	port->con.deattach = typec_partner_deattach;
+
+	if (cap->usb_capability & USB_CAPABILITY_USB4)
+		port->usb_mode = USB_MODE_USB4;
+	else if (cap->usb_capability & USB_CAPABILITY_USB3)
+		port->usb_mode = USB_MODE_USB3;
+	else if (cap->usb_capability & USB_CAPABILITY_USB2)
+		port->usb_mode = USB_MODE_USB2;
 
 	device_initialize(&port->dev);
 	port->dev.class = &typec_class;

drivers/usb/typec/class.h

···
 	enum typec_role			vconn_role;
 	enum typec_pwr_opmode		pwr_opmode;
 	enum typec_port_type		port_type;
+	enum usb_mode			usb_mode;
 	struct mutex			port_type_lock;
 
 	enum typec_orientation		orientation;

include/linux/usb/typec.h

···
 	TYPEC_ORIENTATION_REVERSE,
 };
 
+enum usb_mode {
+	USB_MODE_NONE,
+	USB_MODE_USB2,
+	USB_MODE_USB3,
+	USB_MODE_USB4
+};
+
+#define USB_CAPABILITY_USB2	BIT(0)
+#define USB_CAPABILITY_USB3	BIT(1)
+#define USB_CAPABILITY_USB4	BIT(2)
+
 /*
  * struct enter_usb_data - Enter_USB Message details
  * @eudo: Enter_USB Data Object
···
  * @port_type_set: Set port type
  * @pd_get: Get available USB Power Delivery Capabilities.
  * @pd_set: Set USB Power Delivery Capabilities.
+ * @default_usb_mode_set: USB Mode to be used by default with Enter_USB Message
  */
 struct typec_operations {
 	int (*try_role)(struct typec_port *port, int role);
···
 			     enum typec_port_type type);
 	struct usb_power_delivery **(*pd_get)(struct typec_port *port);
 	int (*pd_set)(struct typec_port *port, struct usb_power_delivery *pd);
+	int (*default_usb_mode_set)(struct typec_port *port, enum usb_mode mode);
 };
 
 enum usb_pd_svdm_ver {
···
  * @svdm_version: USB PD Structured VDM version if supported
  * @prefer_role: Initial role preference (DRP ports).
  * @accessory: Supported Accessory Modes
+ * @usb_capability: Supported USB Modes
  * @fwnode: Optional fwnode of the port
  * @driver_data: Private pointer for driver specific info
  * @pd: Optional USB Power Delivery Support
···
 	int			prefer_role;
 	enum typec_accessory	accessory[TYPEC_MAX_ACCESSORY];
 	unsigned int		orientation_aware:1;
+	u8			usb_capability;
 
 	struct fwnode_handle	*fwnode;
 	void			*driver_data;
···
 int typec_port_set_usb_power_delivery(struct typec_port *port, struct usb_power_delivery *pd);
 int typec_partner_set_usb_power_delivery(struct typec_partner *partner,
 					 struct usb_power_delivery *pd);
+
+void typec_port_set_usb_mode(struct typec_port *port, enum usb_mode mode);
 
 /**
  * struct typec_connector - Representation of Type-C port for external drivers