sim: Integrate simulator into UHD

This commit adds a device::register_device which allows uhd to start up
a simulator when uhd is called with the arguments type=sim. Creating the
device object creates a subprocess using pybind and an embedded
interpreter, and destroying the object cleans up those subprocesses.

Signed-off-by: Samuel O'Brien <sam.obrien@ni.com>

3 files changed, 75 insertions, 2 deletions

diff --git a/mpm/python/usrp_hwd.py b/mpm/python/usrp_hwd.py
index fb8c1b94e..aaa426fc4 100755
--- a/mpm/python/usrp_hwd.py
+++ b/mpm/python/usrp_hwd.py
@@ -24,6 +24,10 @@ from threading import Event, Thread
 
 _PROCESSES = []
 _KILL_EVENT = Event()
+# This Global Variable is used by the Simulator to make the spawn_processes,
+# and by extension the main method, exit without waiting for the simulator to stop.
+# See process_manager.py:bootstrap() for more information.
+JOIN_PROCESSES = True
 
 def setup_arg_parser():
     """
@@ -31,6 +35,12 @@ def setup_arg_parser():
     """
     parser = argparse.ArgumentParser(description="USRP Hardware Daemon")
     parser.add_argument(
+        '--no-logbuf',
+        dest='use_logbuf',
+        help="Do not send log messages to UHD",
+        action="store_false",
+    )
+    parser.add_argument(
         '--daemon',
         help="Run as daemon",
         action="store_true",
@@ -169,8 +179,9 @@ def spawn_processes(log, args):
     Thread(target=kill_thread, daemon=False).start()
     signal.signal(signal.SIGTERM, kill_time)
     signal.signal(signal.SIGINT, kill_time)
-    for proc in _PROCESSES:
-        proc.join()
+    if JOIN_PROCESSES:
+        for proc in _PROCESSES:
+            proc.join()
     return True
 
 def main():
@@ -181,6 +192,7 @@ def main():
     """
     args = parse_args()
     log = mpm.get_main_logger(
+        use_logbuf=args.use_logbuf,
         log_default_delta=args.verbose-args.quiet
     ).getChild('main')
     version_string = mpm.__version__
diff --git a/mpm/python/usrp_mpm/CMakeLists.txt b/mpm/python/usrp_mpm/CMakeLists.txt
index 293892337..f1637ab03 100644
--- a/mpm/python/usrp_mpm/CMakeLists.txt
+++ b/mpm/python/usrp_mpm/CMakeLists.txt
@@ -23,6 +23,7 @@ set(USRP_MPM_TOP_FILES
     ${CMAKE_CURRENT_SOURCE_DIR}/mpmutils.py
     ${CMAKE_CURRENT_SOURCE_DIR}/prefs.py
     ${CMAKE_CURRENT_SOURCE_DIR}/rpc_server.py
+    ${CMAKE_CURRENT_SOURCE_DIR}/process_manager.py
 )
 list(APPEND USRP_MPM_FILES ${USRP_MPM_TOP_FILES})
 add_subdirectory(chips)
diff --git a/mpm/python/usrp_mpm/process_manager.py b/mpm/python/usrp_mpm/process_manager.py
new file mode 100644
index 000000000..eb1215ad7
--- /dev/null
+++ b/mpm/python/usrp_mpm/process_manager.py
@@ -0,0 +1,60 @@
+#
+# Copyright 2020 Ettus Research, a National Instruments Brand
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+"""
+This module is used as an interface between the sim_find.cpp discovery
+and mboard_iface in uhd and the usrp_hwd python file. It manages
+starting and stopping the simulator subprocess and configuring logging
+"""
+from multiprocessing import Process, Event
+import sys
+try:
+    # Location if installed from using make install
+    import usrp_hwd
+except ImportError:
+    # Location if installed from libpyuhd using setuptools
+    from usrp_mpm import usrp_hwd
+
+class ProcessManager:
+    """This object is used to manage a simulator process which is launched
+    from a python interpreter rather than from an os shell or using systemd
+    """
+    def __init__(self, args):
+        """args are the command line arguments received by the simulator"""
+        self.stop_event = Event()
+        self.process = Process(target=_bootstrap, args=[args, self.stop_event])
+
+    def start(self):
+        """Launch the simulator's process"""
+        self.process.start()
+
+    def stop(self, timeout):
+        """Attempt to stop the simulator cleanly. Returns True if successful"""
+        self.stop_event.set()
+        self.process.join(timeout)
+        return self.process.exitcode is not None
+
+    def terminate(self):
+        """Forcefully terminates the simulator"""
+        self.process.terminate()
+
+    def pid(self):
+        """Returns the PID of the simulator subprocess"""
+        return int(self.process.pid)
+
+def _bootstrap(args, stop_event):
+    # Set args for new process
+    #
+    # Disable UHD log forwarding to avoid
+    # duplicate messages
+    sys.argv = ["usrp_hwd.py"] + args + ["--no-logbuf"]
+    # tell main() not to block
+    usrp_hwd.JOIN_PROCESSES = False
+    # Start the discovery and RPC processes
+    usrp_hwd.main()
+    # Wait for signal from other process
+    stop_event.wait()
+    # Stop the discovery and RPC processes
+    usrp_hwd.kill_time(None, None)