From d0b8daa005c332b97e3014576b4e6aabfaeccef1 Mon Sep 17 00:00:00 2001
From: Florent Kermarrec <florent@enjoy-digital.fr>
Date: Tue, 5 May 2020 11:23:46 +0200
Subject: [PATCH] build/platform: allow doing a loose lookup_request (return
 None instead of ConstraintError) and allow subname in lookup_request.

In the platforms, insead of doing:
self.lookup_request("eth_clocks").rx
we can now do:
self.lookup_request("eth_clocks:rx")

This allows some try/except simplifications on constraints.
---
 litex/build/altera/platform.py    |  1 +
 litex/build/generic_platform.py   | 14 +++++++++++---
 litex/build/lattice/platform.py   |  1 +
 litex/build/microsemi/platform.py |  1 +
 litex/build/xilinx/platform.py    |  1 +
 5 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/litex/build/altera/platform.py b/litex/build/altera/platform.py
index a95dcf4b..2f03fc72 100644
--- a/litex/build/altera/platform.py
+++ b/litex/build/altera/platform.py
@@ -33,6 +33,7 @@ class AlteraPlatform(GenericPlatform):
         return self.toolchain.build(self, *args, **kwargs)
 
     def add_period_constraint(self, clk, period):
+        if clk is None: return
         if hasattr(clk, "p"):
             clk = clk.p
         self.toolchain.add_period_constraint(self, clk, period)
diff --git a/litex/build/generic_platform.py b/litex/build/generic_platform.py
index d540cc38..7c489efe 100644
--- a/litex/build/generic_platform.py
+++ b/litex/build/generic_platform.py
@@ -205,13 +205,21 @@ class ConstraintManager:
         self.matched.append((resource, obj))
         return obj
 
-    def lookup_request(self, name, number=None):
+    def lookup_request(self, name, number=None, loose=False):
+        subname = None
+        if ":" in name: name, subname = name.split(":")
         for resource, obj in self.matched:
             if resource[0] == name and (number is None or
                                         resource[1] == number):
-                return obj
+                if subname is not None:
+                    return getattr(obj, subname)
+                else:
+                    return obj
 
-        raise ConstraintError("Resource not found: {}:{}".format(name, number))
+        if loose:
+            return None
+        else:
+            raise ConstraintError("Resource not found: {}:{}".format(name, number))
 
     def add_platform_command(self, command, **signals):
         self.platform_commands.append((command, signals))
diff --git a/litex/build/lattice/platform.py b/litex/build/lattice/platform.py
index 71ff2a65..7380b45e 100644
--- a/litex/build/lattice/platform.py
+++ b/litex/build/lattice/platform.py
@@ -34,6 +34,7 @@ class LatticePlatform(GenericPlatform):
         return self.toolchain.build(self, *args, **kwargs)
 
     def add_period_constraint(self, clk, period):
+        if clk is None: return
         if hasattr(clk, "p"):
             clk = clk.p
         self.toolchain.add_period_constraint(self, clk, period)
diff --git a/litex/build/microsemi/platform.py b/litex/build/microsemi/platform.py
index 65d2c996..c8f13bd8 100644
--- a/litex/build/microsemi/platform.py
+++ b/litex/build/microsemi/platform.py
@@ -28,6 +28,7 @@ class MicrosemiPlatform(GenericPlatform):
         return self.toolchain.build(self, *args, **kwargs)
 
     def add_period_constraint(self, clk, period):
+        if clk is None: return
         clk.attr.add("keep")
         if hasattr(clk, "p"):
             clk = clk.p
diff --git a/litex/build/xilinx/platform.py b/litex/build/xilinx/platform.py
index cf7bbeb5..d5e3d8f8 100644
--- a/litex/build/xilinx/platform.py
+++ b/litex/build/xilinx/platform.py
@@ -48,6 +48,7 @@ class XilinxPlatform(GenericPlatform):
         return self.toolchain.build(self, *args, **kwargs)
 
     def add_period_constraint(self, clk, period):
+        if clk is None: return
         if hasattr(clk, "p"):
             clk = clk.p
         self.toolchain.add_period_constraint(self, clk, period)
-- 
2.30.2