Revert "iso-tp: more checks (#1487)" (#1616)

* Revert "iso-tp: return if updated (#1610)"

This reverts commit 0eb04fa.

* Revert "iso-tp: more sanity checks (#1487)"

This reverts commit 01db9e4.

python/uds.py

@@ -449,18 +449,18 @@ def recv(self, timeout=None) -> Tuple[Optional[bytes], bool]:
       timeout = self.timeout
 
     start_time = time.monotonic()
-    updated = False
+    rx_in_progress = False
     try:
       while True:
         for msg in self._can_client.recv():
-          self._isotp_rx_next(msg)
+          frame_type = self._isotp_rx_next(msg)
           start_time = time.monotonic()
-          updated = True
+          rx_in_progress = frame_type == ISOTP_FRAME_TYPE.CONSECUTIVE
           if self.tx_done and self.rx_done:
-            return self.rx_dat, updated
+            return self.rx_dat, False
         # no timeout indicates non-blocking
         if timeout == 0:
-          return None, updated
+          return None, rx_in_progress
         if time.monotonic() - start_time > timeout:
           raise MessageTimeoutError("timeout waiting for response")
     finally:
@@ -473,7 +473,6 @@ def _isotp_rx_next(self, rx_data: bytes) -> ISOTP_FRAME_TYPE:
     # assert len(rx_data) == self.max_len, f"isotp - rx: invalid CAN frame length: {len(rx_data)}"
 
     if rx_data[0] >> 4 == ISOTP_FRAME_TYPE.SINGLE:
-      assert not self.rx_done, "isotp - rx: unexpected single frame"
       self.rx_len = rx_data[0] & 0x0F
       assert self.rx_len < self.max_len, f"isotp - rx: invalid single frame length: {self.rx_len}"
       self.rx_dat = rx_data[1:1 + self.rx_len]
@@ -484,7 +483,6 @@ def _isotp_rx_next(self, rx_data: bytes) -> ISOTP_FRAME_TYPE:
       return ISOTP_FRAME_TYPE.SINGLE
 
     elif rx_data[0] >> 4 == ISOTP_FRAME_TYPE.FIRST:
-      assert self.rx_dat == b"", "isotp - rx: first frame with data already received"
       self.rx_len = ((rx_data[0] & 0x0F) << 8) + rx_data[1]
       assert self.max_len <= self.rx_len, f"isotp - rx: invalid first frame length: {self.rx_len}"
       self.rx_dat = rx_data[2:]