SPI: add protcol version request (#1488)

* SPI: add protcol version request

* quick test

* fix linter

* misra

---------

Co-authored-by: Comma Device <device@comma.ai>

board/drivers/spi.h

@@ -78,7 +78,31 @@ void spi_rx_done(void) {
   spi_data_len_mosi = (spi_buf_rx[3] << 8) | spi_buf_rx[2];
   spi_data_len_miso = (spi_buf_rx[5] << 8) | spi_buf_rx[4];
 
-  if (spi_state == SPI_STATE_HEADER) {
+  if (memcmp(spi_buf_rx, "VERSION", 7) == 0) {
+    // protocol version request, respond with:
+    // VERSION + 2 byte data length + data + data complement
+
+    // echo "VERSION"
+    (void)memcpy(spi_buf_tx, "VERSION", 7);
+
+    // write response
+    uint16_t data_pos = 9;
+    uint16_t data_len = 1;
+    spi_buf_tx[data_pos] = 0x1;
+
+    // response complement
+    for (uint16_t i = 0U; i < data_len; i++) {
+      spi_buf_tx[data_pos + data_len + i] = spi_buf_tx[data_pos + i] ^ 0xFFU;
+    }
+
+    // data length
+    data_len *= 2U;
+    spi_buf_tx[7] = data_len & 0xFFU;
+    spi_buf_tx[8] = (data_len >> 8) & 0xFFU;
+
+    response_len = 7U + 2U + data_len;
+    next_rx_state = SPI_STATE_HEADER_NACK;;
+  } else if (spi_state == SPI_STATE_HEADER) {
     checksum_valid = check_checksum(spi_buf_rx, SPI_HEADER_SIZE);
     if ((spi_buf_rx[0] == SPI_SYNC_BYTE) && checksum_valid) {
       // response: ACK and start receiving data portion

python/spi.py

@@ -167,6 +167,44 @@ class PandaSpiHandle(BaseHandle):
 
     raise exc
 
+  def get_protocol_version(self) -> bytes:
+    vers_str = b"VERSION"
+    def _get_version(spi) -> bytes:
+      spi.writebytes(vers_str)
+
+      logging.debug("- waiting for echo")
+      start = time.monotonic()
+      while True:
+        r = spi.readbytes(len(vers_str))
+        if bytes(r) == vers_str:
+          break
+        if (time.monotonic() - start) > 0.5:
+          raise PandaSpiException("timed out waiting for version echo")
+
+      # get response
+      logging.debug("- receiving response")
+      b = bytes(spi.readbytes(2))
+      rlen = struct.unpack("<H", b)[0]
+      if rlen > 1000:
+        raise PandaSpiException("response length greater than max")
+
+      dat = bytes(spi.readbytes(rlen))
+      resp = dat[:rlen//2]
+      resp_comp = dat[rlen//2:]
+      if resp != bytes([x ^ 0xff for x in resp_comp]):
+        raise PandaSpiException("data complement doesn't match")
+      return resp
+
+    exc = PandaSpiException()
+    with self.dev.acquire() as spi:
+      for _ in range(10):
+        try:
+          return _get_version(spi)
+        except PandaSpiException as e:
+          exc = e
+          logging.debug("SPI get protocol version failed, retrying", exc_info=True)
+    raise exc
+
   # libusb1 functions
   def close(self):
     self.dev.close()

tests/hitl/8_spi.py

@@ -17,6 +17,10 @@ class TestSpi:
     assert spy.call_count == 2
     mocker.stop(spy)
 
+  def test_protocol_version(self, p):
+    v = p._handle.get_protocol_version()
+    assert v == b"\x01"
+
   def test_all_comm_types(self, mocker, p):
     spy = mocker.spy(p._handle, '_wait_for_ack')