fhdl: compact Instance syntax

doc/fhdl.rst

@@ -139,10 +139,10 @@ A triplet (O, OE, I) of one-way signals defining a tri-state I/O port is represe
 The object that can be used in as a module special is ``Tristate``, and it behaves exactly like an instance of a tri-state I/O buffer that would be defined as follows: ::
 
   Instance("Tristate",
-    Instance.Inout("target", target),
-    Instance.Input("o", o),
-    Instance.Input("oe", oe),
-    Instance.Output("i", i)
+    io_target=target,
+    i_o=o,
+    i_oe=oe,
+    o_i=i
   )
 
 Signals ``target``, ``o`` and ``i`` can have any width, while ``oe`` is 1-bit wide. The ``target`` signal should go to a port and not be used elsewhere in the design. Like modern FPGA architectures, Migen does not support internal tri-states.

examples/basic/arrays.py

@@ -21,6 +21,6 @@ class Example(Module):
 
 		ina = Array(Signal() for a in range(dx))
 		outa = Array(Signal() for a in range(dy))
-		self.specials += Instance("test", Instance.Output("O", outa[y]), Instance.Input("I", ina[x]))
+		self.specials += Instance("test", o_O=outa[y], i_I=ina[x])
 
 print(verilog.convert(Example()))

migen/fhdl/specials.py

@@ -1,3 +1,5 @@
+from operator import itemgetter
+
 from migen.fhdl.structure import *
 from migen.fhdl.size import bits_for, value_bits_sign
 from migen.fhdl.tools import *
@@ -68,15 +70,6 @@ class TSTriple:
 		return Tristate(target, self.o, self.oe, self.i)
 
 class Instance(Special):
-	def __init__(self, of, *items, name=""):
-		Special.__init__(self)
-		self.of = of
-		if name:
-			self.name_override = name
-		else:
-			self.name_override = of
-		self.items = items
-	
 	class _IO:
 		def __init__(self, name, expr=None):
 			self.name = name
@@ -89,12 +82,29 @@ class Instance(Special):
 		pass
 	class InOut(_IO):
 		pass
-
 	class Parameter:
 		def __init__(self, name, value):
 			self.name = name
 			self.value = value
 
+	def __init__(self, of, *items, name="", **kwargs):
+		Special.__init__(self)
+		self.of = of
+		if name:
+			self.name_override = name
+		else:
+			self.name_override = of
+		self.items = list(items)
+		for k, v in sorted(kwargs.items(), key=itemgetter(1)):
+			item_type, item_name = k.split("_", maxsplit=1)
+			item_class = {
+				"i": Instance.Input,
+				"o": Instance.Output,
+				"io": Instance.InOut,
+				"p": Instance.Parameter
+			}[item_type]
+			self.items.append(item_class(item_name, v))
+	
 	def get_io(self, name):
 		for item in self.items:
 			if isinstance(item, Instance._IO) and item.name == name: