fixed message for vhci mode only linux. and changed readme

internal/client/use.go

@@ -91,8 +91,8 @@ func (um *UseManager) GetAttachedDevices() []*AttachedDevice {
 // AttachDevice requests and attaches a remote USB device
 func (um *UseManager) AttachDevice(clientID, busID string) error {
 	// Check if VHCI is available
-	if !usbip.IsVHCIAvailable() {
-		return fmt.Errorf("vhci-hcd kernel module not loaded (run: sudo modprobe vhci-hcd)")
+	if err := usbip.VHCIUnavailableError(); err != nil {
+		return err
 	}
 
 	key := busID + "@" + clientID

internal/usbip/vhci.go

@@ -166,3 +166,12 @@ func IsVHCIAvailable() bool {
 	_, err := os.Stat(vhciBasePath)
 	return err == nil
 }
+
+// VHCIUnavailableError returns an error describing why VHCI is not available,
+// or nil if VHCI is ready to use.
+func VHCIUnavailableError() error {
+	if IsVHCIAvailable() {
+		return nil
+	}
+	return fmt.Errorf("vhci-hcd Kernel-Modul nicht geladen (ausfuehren: sudo modprobe vhci-hcd)")
+}

internal/usbip/vhci_windows.go

@@ -8,6 +8,11 @@ func IsVHCIAvailable() bool {
 	return false
 }
 
+// VHCIUnavailableError returns an error describing why VHCI is not available.
+func VHCIUnavailableError() error {
+	return fmt.Errorf("VHCI wird unter Windows nicht unterstuetzt. Der Use-Modus (USB-Geraete empfangen) ist nur unter Linux verfuegbar")
+}
+
 func FindFreePort(speed uint32) (int, error) {
 	return -1, fmt.Errorf("VHCI not supported on Windows")
 }