begin USB refactor with package machine/usb2

src/machine/usb/config.go

@@ -0,0 +1,25 @@
+package usb
+
+// The following constants must be defined for USB 2.0 host/device support.
+//
+// However, some or all of these constants may be unused in the core driver
+// code, depending on which components are allocated by the USB driver.
+//
+// These values are __PLATFORM-AGNOSTIC__, and they serve two primary roles:
+//   1. Aggregate and export values derived from platform-specific constants.
+//   2. Configure core attributes defined by the USB 2.0 specification.
+//
+const (
+	// ConfigPortCount defines the number of USB cores supported on this platform.
+	ConfigPortCount = configDeviceCount + configHostCount
+)
+
+// ConfigDeviceDescriptor defines the fields used to populate host-enumerated
+// device descriptors.
+type ConfigDeviceDescriptor struct {
+	Manufacturer string
+	Product      string
+	VID          uint16
+	PID          uint16
+	BCD          uint16
+}