usb: common: Small class for USB role switches

USB role switch is a device that can be used to choose the
data role for USB connector. With dual-role capable USB
controllers, the controller itself will be the switch, but
on some platforms the USB host and device controllers are
separate IPs and there is a mux between them and the
connector. On those platforms the mux driver will need to
register the switch.

With USB Type-C connectors, the host-to-device relationship
is negotiated over the Configuration Channel (CC). That
means the USB Type-C drivers need to be in control of the
role switch. The class provides a simple API for the USB
Type-C drivers for the control.

For other types of USB connectors (mainly microAB) the class
provides user space control via sysfs attribute file that
can be used to request role swapping from the switch.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 53 insertions, 0 deletions

diff --git a/include/linux/usb/role.h b/include/linux/usb/role.h
new file mode 100644
index 0000000000000..edc51be4a77c6
--- /dev/null
+++ b/include/linux/usb/role.h
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#ifndef __LINUX_USB_ROLE_H
+#define __LINUX_USB_ROLE_H
+
+#include <linux/device.h>
+
+struct usb_role_switch;
+
+enum usb_role {
+	USB_ROLE_NONE,
+	USB_ROLE_HOST,
+	USB_ROLE_DEVICE,
+};
+
+typedef int (*usb_role_switch_set_t)(struct device *dev, enum usb_role role);
+typedef enum usb_role (*usb_role_switch_get_t)(struct device *dev);
+
+/**
+ * struct usb_role_switch_desc - USB Role Switch Descriptor
+ * @usb2_port: Optional reference to the host controller port device (USB2)
+ * @usb3_port: Optional reference to the host controller port device (USB3)
+ * @udc: Optional reference to the peripheral controller device
+ * @set: Callback for setting the role
+ * @get: Callback for getting the role (optional)
+ * @allow_userspace_control: If true userspace may change the role through sysfs
+ *
+ * @usb2_port and @usb3_port will point to the USB host port and @udc to the USB
+ * device controller behind the USB connector with the role switch. If
+ * @usb2_port, @usb3_port and @udc are included in the description, the
+ * reference count for them should be incremented by the caller of
+ * usb_role_switch_register() before registering the switch.
+ */
+struct usb_role_switch_desc {
+	struct device *usb2_port;
+	struct device *usb3_port;
+	struct device *udc;
+	usb_role_switch_set_t set;
+	usb_role_switch_get_t get;
+	bool allow_userspace_control;
+};
+
+int usb_role_switch_set_role(struct usb_role_switch *sw, enum usb_role role);
+enum usb_role usb_role_switch_get_role(struct usb_role_switch *sw);
+struct usb_role_switch *usb_role_switch_get(struct device *dev);
+void usb_role_switch_put(struct usb_role_switch *sw);
+
+struct usb_role_switch *
+usb_role_switch_register(struct device *parent,
+			 const struct usb_role_switch_desc *desc);
+void usb_role_switch_unregister(struct usb_role_switch *sw);
+
+#endif /* __LINUX_USB_ROLE_H */