fix(dbus): Add error handling for DBus publishing and main loop

Wrap DBus publishing and main loop execution in try-except blocks to
capture and log failures. This ensures better visibility into errors and
prevents silent failures during runtime.

src/revpi_middleware/cli_commands/cli_picontrol.py

@@ -4,7 +4,7 @@
 from argparse import ArgumentParser
 from logging import getLogger
 
-from .dbus_helper import await_signal, simple_call
+from .dbus_helper import BusType, await_signal, simple_call
 from .. import proginit as pi
 from ..dbus_middleware1 import extend_interface
 
@@ -36,12 +36,20 @@ def add_subparsers(parent_parser: ArgumentParser):
 
 def method_reset():
     log.debug("D-Bus call of method ResetDriver")
-    simple_call("ResetDriver", interface=extend_interface("picontrol"))
+    simple_call(
+        "ResetDriver",
+        interface=extend_interface("picontrol"),
+        bus_type=BusType.SESSION if pi.pargs.use_session_bus else BusType.SYSTEM,
+    )
     log.info("ResetDriver called via D-Bus")
 
 
 def method_await_reset(timout: int = 0):
-    detected_signal = await_signal("NotifyDriverReset", timout, extend_interface("picontrol"))
+    detected_signal = await_signal(
+        "NotifyDriverReset",
+        timout, extend_interface("picontrol"),
+        bus_type=BusType.SESSION if pi.pargs.use_session_bus else BusType.SYSTEM,
+    )
     if detected_signal:
         log.info("ResetDriver signal received")
     else:

src/revpi_middleware/cli_commands/dbus_helper.py

@@ -1,46 +1,98 @@
 # SPDX-FileCopyrightText: 2025 KUNBUS GmbH
 # SPDX-License-Identifier: GPL-2.0-or-later
 """D-Bus helper functions for cli commands."""
+from enum import Enum
 from threading import Thread
 from time import sleep
 
 from gi.repository import GLib
-from pydbus import SystemBus
+from pydbus import SessionBus, SystemBus
 
 from ..dbus_middleware1 import REVPI_DBUS_BASE_PATH
 from ..dbus_middleware1 import REVPI_DBUS_NAME
 
-PICONTROL_INTERFACE = "com.revolutionpi.middleware1.picontrol"
-RESET_DRIVER_METHOD = "ResetDriver"
+
+class BusType(Enum):
+    SESSION = "session"
+    SYSTEM = "system"
 
 
-def simple_call(method: str, *args, interface: str, object_path=REVPI_DBUS_BASE_PATH):
+def simple_call(
+    method: str,
+    *args,
+    interface: str,
+    object_path=REVPI_DBUS_BASE_PATH,
+    bus_type=BusType.SYSTEM,
+):
     """
-    Executes a method on a specific D-Bus object interface within the RevPi system. This function
-    connects to the system bus, retrieves the desired interface and object path, and invokes
-    the specified method with provided arguments.
+    Performs a call to a D-Bus method on a specified interface and object.
+
+    This function uses the D-Bus messaging system to dynamically call a method
+    of a specified interface, using the given object path and bus type. It
+    provides a way to interact with D-Bus interfaces, using either a system or
+    session bus, and returns the result of executing the specified method.
 
     Parameters:
     method: str
-        The name of the method to be invoked on the targeted interface.
-    *args: tuple
-        Positional arguments to be passed to the method being invoked.
+        The name of the method to invoke on the D-Bus interface.
+    *args:
+        Additional positional arguments to pass to the specified D-Bus method.
     interface: str
-        The name of the D-Bus interface providing the required functionality.
-    object_path: str, optional
-        The D-Bus object path of the RevPi interface. Defaults to REVPI_DBUS_BASE_PATH.
+        The name of the D-Bus interface containing the method.
+    object_path:
+        The path of the D-Bus object on which the interface is defined. Defaults
+        to REVPI_DBUS_BASE_PATH.
+    bus_type: BusType
+        Specifies whether to use the system or session bus. Defaults to BusType.SYSTEM.
 
     Returns:
-    Any
-        The result of the method invocation on the targeted D-Bus interface.
+        The value returned by the D-Bus method.
+
+    Raises:
+        Any errors raised from the D-Bus call will propagate to the caller.
     """
-    bus = SystemBus()
+    bus = SessionBus() if bus_type is BusType.SESSION else SystemBus()
     revpi = bus.get(REVPI_DBUS_NAME, object_path)
     iface = revpi[interface]
     return getattr(iface, method)(*args)
 
 
-def await_signal(signal_name: str, timeout: int, interface: str, object_path=REVPI_DBUS_BASE_PATH):
+def await_signal(
+    signal_name: str,
+    timeout: int,
+    interface: str,
+    object_path=REVPI_DBUS_BASE_PATH,
+    bus_type=BusType.SYSTEM,
+):
+    """
+    Waits for a specific signal and returns whether the signal was detected.
+
+    This function connects to a D-Bus interface and waits for a specific signal
+    to be emitted. If the signal is not received within the specified timeout
+    period, the function will return False. If the signal is detected within
+    the timeout, the function will return True. It can connect to either the
+    system bus or the session bus, depending on the provided `bus_type`.
+
+    Parameters:
+    signal_name: str
+        The name of the signal to be awaited.
+    timeout: int
+        The maximum time to wait for the signal, in seconds. A value of 0 or
+        less means that there is no timeout.
+    interface: str
+        The name of the D-Bus interface to listen on.
+    object_path
+        The D-Bus object path where the interface resides. Defaults to
+        REVPI_DBUS_BASE_PATH.
+    bus_type
+        The type of D-Bus to connect to. Can be either BusType.SYSTEM or
+        BusType.SESSION. Defaults to BusType.SYSTEM.
+
+    Returns:
+    bool
+        True if the signal was detected within the timeout period, False
+        otherwise.
+    """
     detected_signal = False
     timeout = int(timeout)
     loop = GLib.MainLoop()
@@ -55,7 +107,7 @@ def await_signal(signal_name: str, timeout: int, interface: str, object_path=REV
         detected_signal = True
         loop.quit()
 
-    bus = SystemBus()
+    bus = SessionBus() if bus_type is BusType.SESSION else SystemBus()
     revpi = bus.get(REVPI_DBUS_NAME, object_path)
     iface = revpi[interface]
 

src/revpi_middleware/daemon.py

@@ -42,7 +42,7 @@ class MiddlewareDaemon:
         if self.bus_provider and self.bus_provider.is_alive():
             return
 
-        self.bus_provider = BusProvider()
+        self.bus_provider = BusProvider(use_system_bus=not pi.pargs.use_session_bus)
         self.bus_provider.start()
 
         log.debug("leave MiddlewareDaemon.dbus_start")

src/revpi_middleware/dbus_middleware1/__init__.py

@@ -2,27 +2,7 @@
 # SPDX-FileCopyrightText: 2025 KUNBUS GmbH
 # SPDX-License-Identifier: GPL-2.0-or-later
 """D-Bus middleware version 1 of revpi_middleware."""
-from ..__about__ import __author__, __copyright__, __license__, __version__
+from .dbus_helper import REVPI_DBUS_BASE_PATH, REVPI_DBUS_NAME
+from .dbus_helper import extend_interface
 
-REVPI_DBUS_NAME = "com.revolutionpi.middleware1"
-REVPI_DBUS_BASE_PATH = "/com/revolutionpi/middleware1"
-
-
-def extend_interface(*args) -> str:
-    """
-    Extends an interface name by appending additional segments to a pre-defined base name.
-
-    This function takes multiple arguments, concatenates them with a predefined base
-    interface name, and returns the resulting string, effectively constructing an
-    extended interface name.
-
-    Args:
-        *args: str
-            Components to be appended to the base interface name.
-
-    Returns:
-        str
-            Fully constructed interface name by joining the base interface name with
-            the provided segments.
-    """
-    return ".".join([REVPI_DBUS_NAME, *args])
+from .bus_provider import BusProvider

src/revpi_middleware/dbus_middleware1/bus_provider.py

@@ -6,7 +6,7 @@ from logging import getLogger
 from threading import Thread
 
 from gi.repository import GLib
-from pydbus import SystemBus
+from pydbus import SessionBus, SystemBus
 
 from . import REVPI_DBUS_NAME
 from .process_image import InterfacePiControl
@@ -16,25 +16,44 @@ log = getLogger(__name__)
 
 class BusProvider(Thread):
 
-    def __init__(self):
+    def __init__(
+        self,
+        picontrol_device="/dev/piControl0",
+        config_rsc="/etc/revpi/config.rsc",
+        use_system_bus=True,
+    ):
         log.debug("enter BusProvider.__init__")
         super().__init__()
 
-        self._bus = SystemBus()
+        self._bus = SystemBus() if use_system_bus else SessionBus()
         self._loop = GLib.MainLoop()
 
+        self.picontrol_device = picontrol_device
+        self.config_rsc = config_rsc
+
     def run(self):
         log.debug("enter BusProvider.run")
 
-        self._bus.publish(
-            REVPI_DBUS_NAME,
-            InterfacePiControl(),
-        )
+        try:
+            self._bus.publish(
+                REVPI_DBUS_NAME,
+                InterfacePiControl(self.picontrol_device, self.config_rsc),
+            )
+        except Exception as e:
+            log.error(f"can not publish dbus {REVPI_DBUS_NAME}: {e}")
+
+        try:
+            self._loop.run()
+        except Exception as e:
+            log.error(f"can not run dbus mainloop: {e}")
 
-        self._loop.run()
         log.debug("leave BusProvider.run")
 
     def stop(self):
         log.debug("enter BusProvider.stop")
         self._loop.quit()
         log.debug("leave BusProvider.stop")
+
+    @property
+    def running(self):
+        return self._loop.is_running()

src/revpi_middleware/dbus_middleware1/dbus_helper.py

@@ -0,0 +1,31 @@
+# -*- coding: utf-8 -*-
+# SPDX-FileCopyrightText: 2025 KUNBUS GmbH
+# SPDX-License-Identifier: GPL-2.0-or-later
+"""Helper for dbus."""
+
+from logging import getLogger
+
+log = getLogger(__name__)
+
+REVPI_DBUS_NAME = "com.revolutionpi.middleware1"
+REVPI_DBUS_BASE_PATH = "/com/revolutionpi/middleware1"
+
+
+def extend_interface(*args) -> str:
+    """
+    Extends an interface name by appending additional segments to a pre-defined base name.
+
+    This function takes multiple arguments, concatenates them with a predefined base
+    interface name, and returns the resulting string, effectively constructing an
+    extended interface name.
+
+    Args:
+        *args: str
+            Components to be appended to the base interface name.
+
+    Returns:
+        str
+            Fully constructed interface name by joining the base interface name with
+            the provided segments.
+    """
+    return ".".join([REVPI_DBUS_NAME, *args])

src/revpi_middleware/dbus_middleware1/process_image/interface_picontrol.py

@@ -8,7 +8,7 @@ from logging import getLogger
 
 from pydbus.generic import signal
 
-from ..interface_helper import ResetDriverWatchdog
+from .process_image_helper import ResetDriverWatchdog
 
 log = getLogger(__name__)
 
@@ -27,10 +27,11 @@ class InterfacePiControl:
 
     NotifyDriverReset = signal()
 
-    def __init__(self):
-        self.pi_control = "/dev/piControl0"
+    def __init__(self, picontrol_device: str, config_rsc: str):
+        self.picontrol_device = picontrol_device
+        self.config_rsc = config_rsc
 
-        self.wd_reset_driver = ResetDriverWatchdog(self.pi_control)
+        self.wd_reset_driver = ResetDriverWatchdog(self.picontrol_device)
         self.wd_reset_driver.register_call(self.notify_reset_driver)
 
     def notify_reset_driver(self):
@@ -40,9 +41,9 @@ class InterfacePiControl:
         log.debug("enter InterfacePiControl.ResetDriver")
 
         try:
-            fd = os.open(self.pi_control, os.O_WRONLY)
+            fd = os.open(self.picontrol_device, os.O_WRONLY)
         except Exception as e:
-            log.warning(f"could not open ${self.pi_control} to reset driver")
+            log.warning(f"could not open ${self.picontrol_device} to reset driver")
             raise e
 
         execption = None

src/revpi_middleware/dbus_middleware1/process_image/process_image_helper.py

@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-# SPDX-FileCopyrightText: 2020-2023 Sven Sager
+# SPDX-FileCopyrightText: 2025 KUNBUS GmbH
 # SPDX-License-Identifier: GPL-2.0-or-later
 """
 Helper for the process image.
@@ -7,7 +7,6 @@ Helper for the process image.
 The ResetDriverWatchdog class is a copy of revpipyload project module "watchdogs"
 https://github.com/naruxde/revpipyload/blob/b51c2b617a57cc7d96fd67e1da9f090a0624eacb/src/revpipyload/watchdogs.py
 """
-
 import os
 from fcntl import ioctl
 from logging import getLogger
@@ -19,9 +18,9 @@ log = getLogger(__name__)
 class ResetDriverWatchdog(Thread):
     """Watchdog to catch the reset_driver action."""
 
-    def __init__(self, pi_control_device="/dev/piControl0"):
+    def __init__(self, picontrol_device: str):
         super(ResetDriverWatchdog, self).__init__()
-        self.procimg = pi_control_device
+        self.procimg = picontrol_device
         self.daemon = True
         self._calls = []
         self._exit = False
@@ -35,7 +34,7 @@ class ResetDriverWatchdog(Thread):
         """
         Mainloop of watchdog for reset_driver.
 
-        If the thread can not open the process image or the IOCTL is not
+        If the thread cannot open the process image or the IOCTL is not
         implemented (wheezy), the thread function will stop. The trigger
         property will always return True.
         """
@@ -51,7 +50,7 @@ class ResetDriverWatchdog(Thread):
             )
             return
 
-        # The ioctl will return 2 byte (c-type int)
+        # The ioctl will return 2 bytes (c-type int)
         byte_buff = bytearray(2)
         while not self._exit:
             try:
@@ -73,7 +72,7 @@ class ResetDriverWatchdog(Thread):
     def register_call(self, function):
         """Register a function, if watchdog triggers."""
         if not callable(function):
-            return ValueError("Function is not callable.")
+            raise ValueError("Function is not callable.")
         if function not in self._calls:
             self._calls.append(function)
 
@@ -89,7 +88,7 @@ class ResetDriverWatchdog(Thread):
         log.debug("leave ResetDriverWatchdog.stop()")
 
     def unregister_call(self, function=None):
-        """Remove a function call on watchdog trigger."""
+        """Remove a function from the watchdog trigger."""
         if function is None:
             self._calls.clear()
         elif function in self._calls:

src/revpi_middleware/proginit.py

@@ -9,7 +9,7 @@ __version__ = "1.4.0"
 
 import logging
 import sys
-from argparse import ArgumentParser, Namespace
+from argparse import ArgumentParser, Namespace, SUPPRESS
 from configparser import ConfigParser
 from enum import Enum
 from os import R_OK, W_OK, access, environ, getpid, remove
@@ -262,6 +262,16 @@ parser = ArgumentParser(
     prog=programname,
     description="Program description",
 )
+
+# Use session bus of D-Bus for local testing and development proposes (hidden)
+parser.add_argument(
+    "--use-session-bus",
+    dest="use_session_bus",
+    action="store_true",
+    default=False,
+    help=SUPPRESS,
+)
+
 parser.add_argument("--version", action="version", version=f"%(prog)s {program_version}")
 parser.add_argument(
     "-f",