+ if (usb_serial) {
+ const unsigned char *p;
+
+ /* http://msdn.microsoft.com/en-us/library/windows/hardware/gg487321.aspx */
+ for (p = (unsigned char *)usb_serial; *p != '\0'; p++)
+ if (*p < 0x20 || *p > 0x7f || *p == ',') {
+ usb_serial = NULL;
+ break;
+ }
+ }
+