resource: udev: also suggest ID_USB_INTERFACE_NUM for USBResource

A USB serial device often provides multiple interfaces for the same
serial number. In these cases it is not possible to distinguish
the interfaces solely based on the serial number (ID_SERIAL_SHORT).
However, if additionally the interface number (ID_USB_INTERFACE_NUM)
is provided, it is possible to distinguish all interfaces without
the need of using the full device path (ID_PATH).

Example:

  (...)
  === suggested matches ===
  (...)
  USBSerialPort:
    match:
      ID_SERIAL_SHORT: ABCDEF00001
      ID_USB_INTERFACE_NUM: '00'
  (...)
  === suggested matches ===
  (...)
  USBSerialPort:
    match:
      ID_SERIAL_SHORT: ABCDEF00001
      ID_USB_INTERFACE_NUM: '01'

Signed-off-by: Joerg Hofrichter <joerg.hofrichter@ni.com>

Author: joergho

labgrid/resource/udev.py

@@ -91,12 +91,22 @@ def suggest_match(self, device):
                 suggestions.append({'@ID_PATH': path})
 
         serial = self.device.properties.get('ID_SERIAL_SHORT')
+        interface_num = self.device.properties.get('ID_USB_INTERFACE_NUM')
         if serial:
-            suggestions.append({'ID_SERIAL_SHORT': serial})
+            if interface_num is not None:
+                suggestions.append({'ID_SERIAL_SHORT': serial,
+                                    'ID_USB_INTERFACE_NUM': interface_num})
+            else:
+                suggestions.append({'ID_SERIAL_SHORT': serial})
         elif self.match.get('@SUBSYSTEM', None) == 'usb':
             serial = self._get_usb_device().properties.get('ID_SERIAL_SHORT')
+            interface_num = self._get_usb_device().properties.get('ID_USB_INTERFACE_NUM')
             if serial:
-                suggestions.append({'@ID_SERIAL_SHORT': serial})
+                if interface_num is not None:
+                    suggestions.append({'@ID_SERIAL_SHORT': serial,
+                                        '@ID_USB_INTERFACE_NUM': interface_num})
+                else:
+                    suggestions.append({'@ID_SERIAL_SHORT': serial})
 
         return meta, suggestions