fix open/close FD being unclean after successive open/closes, add associated test

Author: willzhang05

plin/device.py

@@ -41,6 +41,10 @@
 PLIOSETLEDSTATE = IOW(ord('u'), 40, PLINUSBLEDState)
 
 
+class PLINException(Exception):
+    pass
+
+
 class PLIN:
     def __init__(self, interface: str):
         self.interface = interface
@@ -72,19 +76,23 @@ def start(self, mode: PLINMode, baudrate: int = 19200):
         self.mode = mode
         self.baudrate = baudrate
 
-        if not self.fd:
+        if self.fd:
+            raise PLINException("Already connected to PLIN device!")
+        else:
             self.fd = os.open(self.interface, os.O_RDWR)
-
-        self.reset()
-        buffer = PLINUSBInitHardware(self.baudrate, self.mode, 0)
-        self._ioctl(PLIOHWINIT, buffer)
+            self.reset()
+            buffer = PLINUSBInitHardware(self.baudrate, self.mode, 0)
+            self._ioctl(PLIOHWINIT, buffer)
 
     def stop(self):
         '''
         Disconnects from the PLIN device by closing the file descriptor.
         '''
         if self.fd:
             os.close(self.fd)
+            self.fd = None
+        else:
+            raise PLINException("Not connected to PLIN device!")
 
     def set_frame_entry(self,
                         id: int,

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "plin-linux"
-version = "0.0.2"
+version = "0.0.3"
 authors = [
   { name="William Zhang", email="[email protected]" },
 ]

tests/integration/test_plin.py

@@ -3,6 +3,7 @@
 from plin.enums import PLINMode, PLINMessageType, PLINFrameDirection, PLINFrameChecksumType
 from plin.structs import *
 
+
 @pytest.fixture
 def plin_interface():
     return "/dev/plin0"
@@ -47,6 +48,24 @@ def test_start(plin_interface, plin):
     plin.stop()
 
 
+def test_start_stop_start(plin_interface, plin):
+    expected_baudrate = 1000
+    expected_mode = PLINMode.SLAVE
+
+    plin.start(mode=expected_mode, baudrate=expected_baudrate)
+    assert plin.get_baudrate() == expected_baudrate
+    assert plin.get_mode() == expected_mode
+    plin.stop()
+
+    expected_baudrate = 19200
+    expected_mode = PLINMode.MASTER
+
+    plin.start(mode=expected_mode, baudrate=expected_baudrate)
+    assert plin.get_baudrate() == expected_baudrate
+    assert plin.get_mode() == expected_mode
+    plin.stop()
+
+
 def test_read_nonblocking(plin_master_19200):
     assert None == plin_master_19200.read(block=False)