doc: Final tweaks on Python Packaging (#358)

Author: junrushao

docs/concepts/abi_overview.md

@@ -15,7 +15,7 @@
 <!--- specific language governing permissions and limitations -->
 <!--- under the License. -->
 
-# ABI Specification
+# ABI Overview
 
 This section provides an overview of the ABI convention of TVM FFI. The ABI
 is designed around the following key principles:

docs/packaging/python_packaging.rst

@@ -144,6 +144,17 @@ It registry handles type translation, error handling, and metadata.
       def add_one(x: int) -> int: ...
 
 
+.. note::
+
+  Global functions can be retrieved via :py:func:`tvm_ffi.get_global_func` in Python, :cpp:func:`TVMFFIFunctionGetGlobal` in C,
+  or :cpp:func:`tvm::ffi::Function::GetGlobal` in C++.
+
+  .. code-block:: python
+
+    func = tvm_ffi.get_global_func("my_ffi_extension.add_one")
+    func(3)  # -> 4
+
+
 Class
 ~~~~~
 

examples/python_packaging/src/extension.cc

@@ -39,6 +39,13 @@ TVM_FFI_DLL_EXPORT_TYPED_FUNC(add_two, AddTwo);
 // [global_function.begin]
 static int AddOne(int x) { return x + 1; }
 
+TVM_FFI_STATIC_INIT_BLOCK() {
+  namespace refl = tvm::ffi::reflection;
+  refl::GlobalDef()  //
+      .def("my_ffi_extension.add_one", AddOne);
+}
+// [global_function.end]
+
 /*!
  * \brief Raise a runtime error to demonstrate error propagation.
  *
@@ -56,11 +63,9 @@ static void RaiseError(const ffi::String& msg) { TVM_FFI_THROW(RuntimeError) <<
 
 TVM_FFI_STATIC_INIT_BLOCK() {
   namespace refl = tvm::ffi::reflection;
-  refl::GlobalDef()
-      .def("my_ffi_extension.add_one", AddOne)
+  refl::GlobalDef()  //
       .def("my_ffi_extension.raise_error", RaiseError);
 }
-// [global_function.end]
 
 // [object.begin]
 class IntPairObj : public ffi::Object {