build: add DSL for defining platform resources.

nmigen/build/dsl.py

@@ -0,0 +1,82 @@
+__all__ = ["Pins", "Subsignal", "DiffPairs", "Resource"]
+
+
+class Pins:
+    def __init__(self, names, dir="io"):
+        if not isinstance(names, str):
+            raise TypeError("Names must be a whitespace-separated string, not {!r}"
+                            .format(names))
+        self.names = names.split()
+
+        if dir not in ("i", "o", "io"):
+            raise TypeError("Direction must be one of \"i\", \"o\" or \"io\", not {!r}"
+                            .format(dir))
+        self.dir = dir
+
+    def __repr__(self):
+        return "(pins {} {})".format(" ".join(self.names), self.dir)
+
+
+class DiffPairs:
+    def __init__(self, p, n, dir="io"):
+        self.p = Pins(p, dir=dir)
+        self.n = Pins(n, dir=dir)
+
+        if len(self.p.names) != len(self.n.names):
+            raise TypeError("Positive and negative pins must have the same width, but {!r} "
+                            "and {!r} do not"
+                            .format(self.p, self.n))
+
+        self.dir = self.p.dir
+
+    def __repr__(self):
+        return "(diffpairs {} {})".format(self.p, self.n)
+
+
+class Subsignal:
+    def __init__(self, name, *io, extras=()):
+        self.name = name
+
+        if not io:
+            raise TypeError("Missing I/O constraints")
+        for c in io:
+            if not isinstance(c, (Pins, DiffPairs, Subsignal)):
+                raise TypeError("I/O constraint must be one of Pins, DiffPairs or Subsignal, "
+                                "not {!r}"
+                                .format(c))
+        if isinstance(io[0], (Pins, DiffPairs)) and len(io) > 1:
+            raise TypeError("Pins and DiffPairs cannot be followed by more I/O constraints, but "
+                            "{!r} is followed by {!r}"
+                            .format(io[0], io[1]))
+        if isinstance(io[0], Subsignal):
+            for c in io[1:]:
+                if not isinstance(c, Subsignal):
+                    raise TypeError("A Subsignal can only be followed by more Subsignals, but "
+                                    "{!r} is followed by {!r}"
+                                    .format(io[0], c))
+        self.io = io
+
+        for c in extras:
+            if not isinstance(c, str):
+                raise TypeError("Extra constraint must be a string, not {!r}".format(c))
+        self.extras = list(extras)
+
+        if isinstance(self.io[0], Subsignal):
+            for sub in self.io:
+                sub.extras += self.extras
+
+    def __repr__(self):
+        return "(subsignal {} {} {})".format(self.name,
+                                             " ".join(map(repr, self.io)),
+                                             " ".join(self.extras))
+
+
+class Resource(Subsignal):
+    def __init__(self, name, number, *io, extras=()):
+        self.number = number
+        super().__init__(name, *io, extras=extras)
+
+    def __repr__(self):
+        return "(resource {} {} {} {})".format(self.name, self.number,
+                                               " ".join(map(repr, self.io)),
+                                               " ".join(self.extras))