duplicate_pin_override: Debugging tool to permit multiple use pins

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

docs/Config_Reference.md

@@ -1574,6 +1574,22 @@ main printer config file. Wildcards may also be used (eg,
 [include my_other_config.cfg]
 ```
 
+## [duplicate_pin_override]
+
+This tool allows a single micro-controller pin to be defined multiple
+times in a config file without normal error checking. This is intended
+for diagnostic and debugging purposes. This section is not needed
+where Klipper supports using the same pin multiple times, and using
+this override may cause confusing and unexpected results.
+
+```
+[duplicate_pin_override]
+pins:
+#   A comma separated list of pins that may be used multiple times in
+#   a config file without normal error checks. This parameter must be
+#   provided.
+```
+
 # Bed probing hardware
 
 ## [probe]

klippy/extras/duplicate_pin_override.py

@@ -0,0 +1,15 @@
+# Tool to disable config checks for duplicate pins
+#
+# Copyright (C) 2021  Kevin O'Connor <kevin@koconnor.net>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+
+class PrinterDupPinOverride:
+    def __init__(self, config):
+        printer = config.get_printer()
+        ppins = printer.lookup_object('pins')
+        for pin_desc in config.get('pins').split(','):
+            ppins.allow_multi_use_pin(pin_desc)
+
+def load_config(config):
+    return PrinterDupPinOverride(config)

klippy/pins.py

@@ -205,6 +205,7 @@ class PrinterPins:
         self.chips = {}
         self.active_pins = {}
         self.pin_resolvers = {}
+        self.allow_multi_use_pins = {}
     def parse_pin(self, pin_desc, can_invert=False, can_pullup=False):
         desc = pin_desc.strip()
         pullup = invert = 0
@@ -241,9 +242,11 @@ class PrinterPins:
         share_name = "%s:%s" % (pin_params['chip_name'], pin)
         if share_name in self.active_pins:
             share_params = self.active_pins[share_name]
-            if share_type is None or share_type != share_params['share_type']:
+            if share_name in self.allow_multi_use_pins:
+                pass
+            elif share_type is None or share_type != share_params['share_type']:
                 raise error("pin %s used multiple times in config" % (pin,))
-            if (pin_params['invert'] != share_params['invert']
+            elif (pin_params['invert'] != share_params['invert']
                   or pin_params['pullup'] != share_params['pullup']):
                 raise error("Shared pin %s must have same polarity" % (pin,))
             return share_params
@@ -268,6 +271,10 @@ class PrinterPins:
             raise error("Duplicate chip name '%s'" % (chip_name,))
         self.chips[chip_name] = chip
         self.pin_resolvers[chip_name] = PinResolver()
+    def allow_multi_use_pin(self, pin_desc):
+        pin_params = self.parse_pin(pin_desc)
+        share_name = "%s:%s" % (pin_params['chip_name'], pin_params['pin'])
+        self.allow_multi_use_pins[share_name] = True
 
 def add_printer_objects(config):
     config.get_printer().add_object('pins', PrinterPins())