check_compliance: check for underscores in property names

Issue failures when a devicetree property defined in a binding
contains an underscore. The standard word separator in a property is a
dash.

(This won't affect the standard -- albeit deprecated -- device_type
property, because that is not defined in any bindings.)

Add an 'allowlist' type file, check_compliance_ok_properties.yaml,
for existing cases that are OK.

Fixes: #53506
Signed-off-by: Marti Bolivar <[email protected]>

Author: mbolivar-nordic

scripts/ci/check_compliance.py

@@ -19,6 +19,7 @@
 import shlex
 
 from yamllint import config, linter
+import yaml
 
 from junitparser import TestCase, TestSuite, JUnitXml, Skipped, Error, Failure
 import magic
@@ -247,6 +248,8 @@ def run(self):
             if len(matches) == 0:
                 self.failure(output)
 
+with open(Path(__file__).parent / 'check_compliance_ok_properties.yaml', 'r') as f:
+    DT_OK_PROPERTIES = set(yaml.safe_load(f.read()))
 
 class DevicetreeBindingsCheck(ComplianceTest):
     """
@@ -285,6 +288,7 @@ def run(self, full=True):
         # This does a bit more work than necessary, but that should
         # be OK.
         for binding in edtlib.bindings_from_dirs(bindings_dirs):
+            self.check_recursively(binding, self.property_name_check)
             self.check_recursively(binding, self.required_false_check)
 
     @staticmethod
@@ -293,6 +297,20 @@ def check_recursively(binding, check_function):
             check_function(binding)
             binding = binding.child_binding
 
+    def property_name_check(self, binding):
+        for prop_name in binding.prop2specs:
+            if '_' in prop_name and prop_name not in DT_OK_PROPERTIES:
+                better_prop = prop_name.replace('_', '-')
+                self.failure(
+                    f'{binding.path}: property "{prop_name}" contains '
+                    'underscores.\n'
+                    f'\tUse "{better_prop}" instead unless '
+                    'this property name is from Linux or another authoritative '
+                    f'upstream source of bindings for compatible "{binding.compatible}".\n'
+                    '\tHint: update check_compliance_ok_properties.yaml if you need to '
+                    'override this check for this property.'
+                )
+
     def required_false_check(self, binding):
         raw_props = binding.raw.get('properties', {})
         for prop_name, raw_prop in raw_props.items():

scripts/ci/check_compliance_ok_properties.yaml

@@ -0,0 +1,9 @@
+# This file is a YAML list of property names that are OK to contain
+# underscores because they are from upstream Linux or some other
+# authoritative source.
+#
+# Otherwise, the preferred word separator in DT property names is '-',
+# not '_'.
+
+- mmc-hs200-1_8v
+- mmc-hs400-1_8v