more docs

Author: tqchen

docs/api/python/target.rst

@@ -2,6 +2,7 @@ tvm.target
 ----------
 .. automodule:: tvm.target
 
+.. autofunction:: tvm.target.generic_func
 
 .. autoclass:: tvm.target.Target
     :members:

python/tvm/target.py

@@ -139,10 +139,38 @@ def __exit__(self, ptype, value, trace):
 def generic_func(fdefault):
     """Wrap a target generic function.
 
+    Generic function allows registeration of further functions
+    that can be dispatched on current target context.
+    If no registered dispatch is matched, the fdefault will be called.
+
     Parameters
     ----------
     fdefault : function
         The default function.
+
+    Returns
+    -------
+    fgeneric : function
+        A wrapped generic function.
+
+    Example
+    -------
+    .. code-block:: python
+
+      import tvm
+      # wrap function as target generic
+      @tvm.target.generic_func
+      def my_func(a):
+          return a + 1
+      # register specialization of my_func under target cuda
+      @my_func.register("cuda")
+      def my_func_cuda(a):
+          return a + 2
+      # displays 3, because my_func is called
+      print(my_func(2))
+      # displays 4, because my_func_cuda is called
+      with tvm.target.cuda():
+          print(my_func(2))
     """
     dispatch_dict = {}
     func_name = fdefault.__name__