edtlib: support inferring binding from node content

doc/guides/dts/bindings.rst

@@ -11,8 +11,9 @@ particular devicetree are useful to :ref:`device drivers <device_model_api>` or
 
 *Devicetree bindings* provide the other half of this information. Zephyr
 devicetree bindings are YAML files in a custom format (Zephyr does not use the
-dt-schema tools used by the Linux kernel). The build system uses bindings
-when generating code for :ref:`dt-from-c`.
+dt-schema tools used by the Linux kernel). With one exception in
+:ref:`dt-inferred-bindings` the build system uses bindings when generating
+code for :ref:`dt-from-c`.
 
 .. _dt-binding-compat:
 
@@ -73,3 +74,32 @@ Below is a template that shows the Zephyr bindings file syntax. It is stored in
 
 .. literalinclude:: ../../../dts/binding-template.yaml
    :language: yaml
+
+.. _dt-inferred-bindings:
+
+Inferred bindings
+*****************
+
+For sample code and applications it can be inconvenient to define a devicetree
+binding when only a few simple properties are needed, such as the identify of
+a GPIO for an application task.  The devicetree syntax allows inference of a
+binding for properties based on the value observed.  This inference is
+supported only for the ``/zephyr,user`` node.  The properties referenced can
+be accessed through the standard devicetree macros,
+e.g. ``DT_PROP(DT_PATH(zephyr_user), bytes)``.
+
+.. code-block:: DTS
+
+   / {
+	zephyr,user {
+		boolean;
+		bytes = [81 82 83];
+		number = <23>;
+		numbers = <1>, <2>, <3>;
+		string = "text";
+		strings = "a", "b", "c";
+		handle = <&gpio0>;
+		handles = <&gpio0>, <&gpio1>;
+		signal-gpios = <&gpio0 1 GPIO_ACTIVE_HIGH>;
+	};
+   };

scripts/dts/edtlib.py

@@ -83,8 +83,9 @@
 except ImportError:
     from yaml import Loader
 
-from dtlib import DT, DTError, to_num, to_nums, TYPE_EMPTY, TYPE_NUMS, \
-                  TYPE_PHANDLE, TYPE_PHANDLES_AND_NUMS
+from dtlib import DT, DTError, to_num, to_nums, TYPE_EMPTY, TYPE_BYTES, \
+                  TYPE_NUM, TYPE_NUMS, TYPE_STRING, TYPE_STRINGS, \
+                  TYPE_PHANDLE, TYPE_PHANDLES, TYPE_PHANDLES_AND_NUMS
 from grutils import Graph
 
 
@@ -157,9 +158,9 @@ class EDT:
     def __init__(self, dts, bindings_dirs, warn_file=None,
                  warn_reg_unit_address_mismatch=True,
                  default_prop_types=True,
-                 support_fixed_partitions_on_any_bus=True):
-        """
-        EDT constructor. This is the top-level entry point to the library.
+                 support_fixed_partitions_on_any_bus=True,
+                 infer_binding_for_paths=None):
+        """EDT constructor. This is the top-level entry point to the library.
 
         dts:
           Path to devicetree .dts file
@@ -184,6 +185,12 @@ def __init__(self, dts, bindings_dirs, warn_file=None,
           If True, set the Node.bus for 'fixed-partitions' compatible nodes
           to None.  This allows 'fixed-partitions' binding to match regardless
           of the bus the 'fixed-partition' is under.
+
+        infer_binding_for_paths (default: None):
+          An iterable of devicetree paths identifying nodes for which bindings
+          should be inferred from the node content.  (Child nodes are not
+          processed.)  Pass none if no nodes should support inferred bindings.
+
         """
         # Do this indirection with None in case sys.stderr is
         # deliberately overridden. We'll only hold on to this file
@@ -193,6 +200,7 @@ def __init__(self, dts, bindings_dirs, warn_file=None,
         self._warn_reg_unit_address_mismatch = warn_reg_unit_address_mismatch
         self._default_prop_types = default_prop_types
         self._fixed_partitions_no_bus = support_fixed_partitions_on_any_bus
+        self._infer_binding_for_paths = set(infer_binding_for_paths or [])
 
         self.dts_path = dts
         self.bindings_dirs = bindings_dirs
@@ -957,6 +965,10 @@ def _init_binding(self):
         # initialized, which is guaranteed by going through the nodes in
         # node_iter() order.
 
+        if self.path in self.edt._infer_binding_for_paths:
+            self._binding_from_properties()
+            return
+
         if self.compats:
             on_bus = self.on_bus
 
@@ -984,6 +996,43 @@ def _init_binding(self):
         # No binding found
         self._binding = self.binding_path = self.matching_compat = None
 
+    def _binding_from_properties(self):
+        # Returns a binding synthesized from the properties in the node.
+
+        if self.compats:
+            _err(f"compatible in node with inferred binding: {self.path}")
+
+        self._binding = OrderedDict()
+        self.matching_compat = self.path.split('/')[-1]
+        self.compats = [self.matching_compat]
+        self.binding_path = None
+
+        properties = OrderedDict()
+        self._binding["properties"] = properties
+        for name, prop in self._node.props.items():
+            pp = OrderedDict()
+            properties[name] = pp
+            if prop.type == TYPE_EMPTY:
+                pp["type"] = "boolean"
+            elif prop.type == TYPE_BYTES:
+                pp["type"] = "uint8-array"
+            elif prop.type == TYPE_NUM:
+                pp["type"] = "int"
+            elif prop.type == TYPE_NUMS:
+                pp["type"] = "array"
+            elif prop.type == TYPE_STRING:
+                pp["type"] = "string"
+            elif prop.type == TYPE_STRINGS:
+                pp["type"] = "string-array"
+            elif prop.type == TYPE_PHANDLE:
+                pp["type"] = "phandle"
+            elif prop.type == TYPE_PHANDLES:
+                pp["type"] = "phandles"
+            elif prop.type == TYPE_PHANDLES_AND_NUMS:
+                pp["type"] = "phandle-array"
+            else:
+                _err(f"cannot infer binding from property: {prop}")
+
     def _binding_from_parent(self):
         # Returns the binding from 'child-binding:' in the parent node's
         # binding (or from the legacy 'sub-node:' key), or None if missing

scripts/dts/gen_defines.py

@@ -39,7 +39,8 @@ def main():
                          # Suppress this warning if it's suppressed in dtc
                          warn_reg_unit_address_mismatch=
                              "-Wno-simple_bus_reg" not in args.dtc_flags,
-                         default_prop_types=True)
+                         default_prop_types=True,
+                         infer_binding_for_paths=["/zephyr,user"])
     except edtlib.EDTError as e:
         sys.exit(f"devicetree error: {e}")
 
@@ -178,10 +179,16 @@ def write_node_comment(node):
 """
 
     if node.matching_compat:
-        s += f"""
+        if node.binding_path:
+            s += f"""
 Binding (compatible = {node.matching_compat}):
   {relativize(node.binding_path)}
 """
+        else:
+            s += f"""
+Binding (compatible = {node.matching_compat}):
+  No yaml (bindings inferred from properties)
+"""
 
     s += f"\nDependency Ordinal: {node.dep_ordinal}\n"
 

scripts/dts/gen_legacy_defines.py

@@ -121,9 +121,15 @@ def write_node_comment(node):
   {node.path}
 """
     if node.matching_compat:
-        s += f"""
+        if node.binding_path:
+            s += f"""
 Binding (compatible = {node.matching_compat}):
   {relativize(node.binding_path)}
+"""
+        else:
+            s += f"""
+Binding (compatible = {node.matching_compat}):
+  No yaml (bindings inferred from properties)
 """
     else:
         s += "\nNo matching binding.\n"

scripts/dts/test.dts

@@ -361,6 +361,22 @@
 		};
 	};
 
+	//
+	// zephyr,user binding inference
+	//
+
+	zephyr,user {
+		boolean;
+		bytes = [81 82 83];
+		number = <23>;
+		numbers = <1>, <2>, <3>;
+		string = "text";
+		strings = "a", "b", "c";
+		handle = <&{/props/ctrl-1}>;
+		phandles = <&{/props/ctrl-1}>, <&{/props/ctrl-2}>;
+		phandle-array-foos = <&{/props/ctrl-2} 1 2>;
+	};
+
 	//
 	// For testing that neither 'include: [foo.yaml, bar.yaml]' nor
 	// 'include: [bar.yaml, foo.yaml]' causes errors when one of the files

scripts/dts/testedtlib.py

@@ -215,6 +215,18 @@ def run():
     verify_streq(edt.get_node("/defaults").props,
                  r"OrderedDict([('int', <Property, name: int, type: int, value: 123>), ('array', <Property, name: array, type: array, value: [1, 2, 3]>), ('uint8-array', <Property, name: uint8-array, type: uint8-array, value: b'\x89\xab\xcd'>), ('string', <Property, name: string, type: string, value: 'hello'>), ('string-array', <Property, name: string-array, type: string-array, value: ['hello', 'there']>), ('default-not-used', <Property, name: default-not-used, type: int, value: 234>)])")
 
+    #
+    # Test binding inference
+    #
+
+    verify_streq(edt.get_node("/zephyr,user").props, r"OrderedDict()")
+
+    edt = edtlib.EDT("test.dts", ["test-bindings"], warnings,
+                     infer_binding_for_paths=["/zephyr,user"])
+
+    verify_streq(edt.get_node("/zephyr,user").props,
+                 r"OrderedDict([('boolean', <Property, name: boolean, type: boolean, value: True>), ('bytes', <Property, name: bytes, type: uint8-array, value: b'\x81\x82\x83'>), ('number', <Property, name: number, type: int, value: 23>), ('numbers', <Property, name: numbers, type: array, value: [1, 2, 3]>), ('string', <Property, name: string, type: string, value: 'text'>), ('strings', <Property, name: strings, type: string-array, value: ['a', 'b', 'c']>), ('handle', <Property, name: handle, type: phandle, value: <Node /props/ctrl-1 in 'test.dts', binding test-bindings/phandle-array-controller-1.yaml>>), ('phandles', <Property, name: phandles, type: phandles, value: [<Node /props/ctrl-1 in 'test.dts', binding test-bindings/phandle-array-controller-1.yaml>, <Node /props/ctrl-2 in 'test.dts', binding test-bindings/phandle-array-controller-2.yaml>]>), ('phandle-array-foos', <Property, name: phandle-array-foos, type: phandle-array, value: [<ControllerAndData, controller: <Node /props/ctrl-2 in 'test.dts', binding test-bindings/phandle-array-controller-2.yaml>, data: OrderedDict([('one', 1), ('two', 2)])>]>)])")
+
     #
     # Test having multiple directories with bindings, with a different .dts file
     #