protocol: use a MisingReplyError instead of timeout exceptions

It's caused by a timeout but the underlying issue is that we never got the
reply that we wanted.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

tuhi/protocol.py

@@ -344,6 +344,18 @@ class ProtocolError(Exception):
         self.message = message
 
 
+class MissingReplyError(ProtocolError):
+    '''
+    Thrown when we expected a reply but never got one. Usually caused by a
+    timeout.
+    '''
+    def __init__(self, request, message=None):
+        self.request = request
+
+    def __repr__(self):
+        return f'Missing reply for request {self.request}. {self.message}'
+
+
 class AuthorizationError(ProtocolError):
     '''
     The device does not recognize our UUID.
@@ -514,6 +526,8 @@ class Msg(object):
                                     timeout=self.timeout or None,
                                     userdata=self.userdata)
         if self.requires_reply:
+            if self.reply is None:
+                raise MissingReplyError(self.request)
             try:
                 self._handle_reply(self.reply)
                 # no exception? we can assume success

tuhi/wacom.py

@@ -24,7 +24,7 @@ from gi.repository import GObject
 from .drawing import Drawing
 from .uhid import UHIDDevice
 import tuhi.protocol
-from tuhi.protocol import NordicData, Interactions, Mode, ProtocolVersion, StrokeFile, UnexpectedDataError, DeviceError
+from tuhi.protocol import NordicData, Interactions, Mode, ProtocolVersion, StrokeFile, UnexpectedDataError, DeviceError, MissingReplyError
 from .util import list2hex, flatten
 from tuhi.config import TuhiConfig
 
@@ -250,10 +250,6 @@ class WacomException(Exception):
     errno = errno.ENOSYS
 
 
-class WacomTimeoutException(WacomException):
-    errno = errno.ETIME
-
-
 class WacomPacket(GObject.Object):
     '''
     A single protocol packet of variable length. The protocol format is a
@@ -367,8 +363,8 @@ class WacomProtocolLowLevelComm(GObject.Object):
 
     def wait_nordic_data(self, expected_opcode, timeout=None):
         if not self.nordic_event.acquire(timeout=timeout):
-            # timeout
-            raise WacomTimeoutException(f'{self.device.name}: Timeout while reading data')
+            logger.error(f'{self.device.name}: Timeout while reading data')
+            return None
 
         data = self.pop_next_message()
 
@@ -622,14 +618,12 @@ class WacomProtocolBase(WacomProtocolLowLevelComm):
     def wait_nordic_unless_pen_data(self, opcode, timeout=None):
         data = None
         while data is None:
-            try:
-                data = self.wait_nordic_data(opcode, timeout)
-            except WacomTimeoutException:
-                # timeout is a time in seconds here
-                if time.time() - self._last_pen_data_time < timeout:
-                    # we timed out, but we are still fetching offline pen data
-                    continue
-                raise
+            data = self.wait_nordic_data(opcode, timeout)
+            # timeout is a time in seconds here
+            # if we exceeded the timeout, we return None, otherwise we keep
+            # looping until we have what we want
+            if time.time() - self._last_pen_data_time > timeout:
+                break
 
         return data
 
@@ -639,7 +633,7 @@ class WacomProtocolBase(WacomProtocolLowLevelComm):
             try:
                 msg = self.p.execute(Interactions.WAIT_FOR_END_READ)
                 break
-            except WacomTimeoutException as e:
+            except MissingReplyError as e:
                 # if we're still reading pen data, try again
                 if time.time() - self._last_pen_data_time > timeout:
                     raise e