Disallow claim of USBDriver with non-NULL device, even if on available_drivers list

USBHost_t36.h

 
 	// The device this object instance is bound to.  In words, this
 	// is the specific device this driver is using.  When not bound
-	// to any device, this must be NULL.
+	// to any device, this must be NULL.  Drivers may set this to
+	// any non-NULL value if they are in a state where they do not
+	// wish to claim any device or interface (eg, if getting data
+	// from the HID parser).
 	Device_t *device;
 
 	friend class USBHost;

enumeration.cpp

 
 	// first check if any driver wishes to claim the entire device
 	for (driver=available_drivers; driver != NULL; driver = driver->next) {
+		if (driver->device != NULL) continue;
 		if (driver->claim(dev, 0, enumbuf + 9, enumlen - 9)) {
 			if (prev) {
 				prev->next = driver->next;
 			// found an interface, ask available drivers if they want it
 			prev = NULL;
 			for (driver=available_drivers; driver != NULL; driver = driver->next) {
+				if (driver->device != NULL) continue;
 				// TODO: should parse ahead and give claim()
 				// an accurate length.  (end - p) is the rest
 				// of ALL descriptors, likely more interfaces
 	for (USBDriver *p = dev->drivers; p; ) {
 		println("disconnect driver ", (uint32_t)p, HEX);
 		p->disconnect();
+		p->device = NULL;
 		USBDriver *next = p->next;
 		p->next = available_drivers;
 		available_drivers = p;