begin USB refactor with package machine/usb2

src/machine/usb2/uart.go

@@ -0,0 +1,53 @@
+package usb2
+
+import (
+	"errors"
+)
+
+var (
+	ErrInvalidPort = errors.New("invalid USB port")
+)
+
+type (
+	UARTConfig struct {
+		BaudRate uint32
+	}
+
+	// UART represents a virtual serial (UART) device emulation using the USB
+	// CDC-ACM device class driver.
+	UART struct {
+		port int // USB port (core index, e.g., 0-1)
+		core *core
+	}
+)
+
+func (uart *UART) Configure(config UARTConfig) error {
+
+	if uart.port >= CoreCount || uart.port >= dciCount ||
+		uart.port >= descCDCACMConfigCount {
+		return ErrInvalidPort
+	}
+
+	// use default configuration index (1-based index; 0=invalid)
+	// uart.config = configDeviceCDCACMConfigurationIndex
+
+	// modify the global basic configuration struct configDeviceCDCACM for our USB
+	// port and configuration index.
+	//
+	// these settings are copied into the real CDC-ACM object, using interface
+	// deviceClassDriver, via initialization method (*deviceCDCACM).init().
+
+	// change baud rate from default, if provided
+	//if config.BaudRate != 0 {
+	//	configDeviceCDCACM[uart.port][uart.config-1].lineCodingBaudRate =
+	//		config.BaudRate
+	//}
+
+	// verify we have a free USB port and take ownership of it
+	var st status
+	uart.core, st = initCore(uart.port, modeDevice)
+	if !st.ok() {
+		return ErrInvalidPort
+	}
+	return nil
+}