python: Add windows dll import logic

In python3.8, a change was made to the DLL search path, which requires using os.add_dll_directory to add a non-default path.

host/python/CMakeLists.txt

@@ -196,11 +196,17 @@ if(ENABLE_SIM)
     set(PYUHD_FILES ${PYUHD_FILES} copy_mpm_packages)
 endif(ENABLE_SIM)
 
-# This copies the contents of host/python/uhd into the build directory. We will
-# use that as a staging ground for installing the final module to the system.
+# This sets the UHD_INSTALL_PATH variable in the __init__.py file so that the UHD python module can find the UHD library.
+set(UHD_INSTALL_PATH ${CMAKE_INSTALL_PREFIX})
+set(UHD_INIT_IN "${CMAKE_CURRENT_SOURCE_DIR}/uhd/__init__.py.in")
+set(UHD_INIT "${CMAKE_CURRENT_BINARY_DIR}/uhd/__init__.py")
+configure_file(${UHD_INIT_IN} ${UHD_INIT} @ONLY)
+
+# This copies the *.py and *.mako files of host/python/uhd into the build directory. 
+# We will use that as a staging ground for installing the final module to the system.
 # We make sure that we always have an up-to-date copy in here.
 add_custom_command(OUTPUT ${TIMESTAMP_FILE}
-  COMMAND ${CMAKE_COMMAND} -E copy_directory ${CMAKE_CURRENT_SOURCE_DIR}/uhd ${CMAKE_CURRENT_BINARY_DIR}/uhd
+  COMMAND ${CMAKE_COMMAND} -DSOURCE_DIR="${CMAKE_CURRENT_SOURCE_DIR}" -DBINARY_DIR="${CMAKE_CURRENT_BINARY_DIR}" -P ${CMAKE_CURRENT_SOURCE_DIR}/copy_python_module.cmake
   COMMAND ${PYTHON_EXECUTABLE} ${SETUP_PY} -q build
   COMMAND ${CMAKE_COMMAND} -E touch ${TIMESTAMP_FILE}
   DEPENDS ${PYUHD_FILES})

host/python/copy_python_module.cmake

@@ -0,0 +1,11 @@
+#
+# Copyright 2024 Ettus Research, a National Instruments Company
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+
+########################################################################
+set(BINARY_DIR "" CACHE STRING "")
+set(SOURCE_DIR "" CACHE STRING "")
+file(COPY "${SOURCE_DIR}/uhd/" DESTINATION "${BINARY_DIR}/uhd"
+    FILES_MATCHING PATTERN "*.py" PATTERN "*.mako")

host/python/uhd/__init__.py

@@ -1,22 +0,0 @@
-#
-# Copyright 2017-2018 Ettus Research, a National Instruments Company
-#
-# SPDX-License-Identifier: GPL-3.0-or-later
-#
-"""
-UHD Python API module
-"""
-
-from . import types
-from . import usrp
-from . import usrpctl
-from . import filters
-from . import rfnoc
-from . import dsp
-from . import chdr
-from .libpyuhd.paths import *
-from .libpyuhd import find
-from .libpyuhd import get_version_string, get_abi_string, get_component
-from .property_tree import PropertyTree
-
-__version__ = get_version_string()

host/python/uhd/__init__.py.in

@@ -0,0 +1,35 @@
+#
+# Copyright 2017-2018 Ettus Research, a National Instruments Company
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+"""UHD Python API module."""
+
+import os
+
+# As of python3.8, python stopped using PATH to search for DLLs on Windows, and
+# required the use of os.add_dll_directory to add paths to the DLL search.
+if os.name == "nt" and hasattr(os, "add_dll_directory"):
+    # The UHD_PKG_PATH will be set if UHD was installed with a UHD NSIS installer, use this path to
+    # find the uhd.dll and add it to the DLL search.
+    uhd_pkg_dir = os.environ.get("UHD_PKG_PATH")
+    if uhd_pkg_dir is not None and os.path.exists(os.path.join(uhd_pkg_dir, "bin", "uhd.dll")):
+        os.add_dll_directory(os.path.join(uhd_pkg_dir, "bin"))
+    else:
+        # If UHD_PKG_PATH is not set, the UHD may have been built and installed from source.
+        # CMake will generate the UHD_INSTALL_PATH variable in the config_vars.py file using the
+        # CMAKE_INSTALL_PREFIX, try to find the uhd.dll with this path.
+        UHD_INSTALL_PATH = "@UHD_INSTALL_PATH@"
+        if os.path.exists(os.path.join(UHD_INSTALL_PATH, "bin", "uhd.dll")):
+            os.add_dll_directory(os.path.join(UHD_INSTALL_PATH, "bin"))
+        else:
+            print(
+                "Failed to add uhd.dll path to DLL search, module may not import properly, use os.add_dll_directory to add the correct path manually."
+            )
+
+from . import chdr, dsp, filters, rfnoc, types, usrp, usrpctl
+from .libpyuhd import find, get_abi_string, get_component, get_version_string
+from .libpyuhd.paths import *  # noqa: F403
+from .property_tree import PropertyTree
+
+__version__ = get_version_string()

mpm/python/copy_python_module.cmake

@@ -1,3 +1,10 @@
+#
+# Copyright 2017 Ettus Research, a National Instruments Company
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+
+########################################################################
 set(BINARY_DIR "" CACHE STRING "")
 set(SOURCE_DIR "" CACHE STRING "")
 file(COPY "${SOURCE_DIR}/usrp_mpm/" DESTINATION ${BINARY_DIR}/usrp_mpm