Add ProbeDevice.

UsbSerialLibrary/src/com/hoho/android/usbserial/driver/UsbSerialProber.java

@@ -67,6 +67,22 @@ public class UsbSerialProber {
         final List<UsbSerialDriver> result = new ArrayList<UsbSerialDriver>();
 
         for (final UsbDevice usbDevice : usbManager.getDeviceList().values()) {
+            final UsbSerialDriver driver = probeDevice(usbDevice);
+            if (driver != null) {
+                result.add(driver);
+            }
+        }
+        return result;
+    }
+    
+    /**
+     * Probes a single device for a compatible driver.
+     * 
+     * @param usbDevice the usb device to probe
+     * @return a new {@link UsbSerialDriver} compatible with this device, or
+     *         {@code null} if none available.
+     */
+    public UsbSerialDriver probeDevice(final UsbDevice usbDevice) {
         final int vendorId = usbDevice.getVendorId();
         final int productId = usbDevice.getProductId();
 
@@ -89,10 +105,9 @@ public class UsbSerialProber {
             } catch (InvocationTargetException e) {
                 throw new RuntimeException(e);
             }
-                result.add(driver);
+            return driver;
         }
-        }
+        return null;
-        return result;
     }
 
 }