Add script for checking resulting kernel config

.github/workflows/build.yaml

@@ -224,6 +224,15 @@ jobs:
             ${{ needs.prepare.outputs.build_container_image }} \
             make BUILDDIR=/build ${{ matrix.board.defconfig }}
 
+      - name: Check Linux config
+        run: |
+          docker run --rm --privileged -v "${GITHUB_WORKSPACE}:/build" \
+            -e BUILDER_UID="$(id -u)" -e BUILDER_GID="$(id -g)" \
+            -v "/mnt/cache:/cache" \
+            ${{ needs.prepare.outputs.build_container_image }} \
+            make -C buildroot O="/build/output" BR2_EXTERNAL="/build/buildroot-external" \
+            BR2_CHECK_DOTCONFIG_OPTS="--github-format --strip-path-prefix=/build/" linux-check-dotconfig
+
       - name: Upload artifacts
         if: ${{ github.event_name != 'release' && needs.prepare.outputs.publish_build == 'true' }}
         working-directory: output/images/

buildroot-external/external.mk

@@ -1 +1,12 @@
 include $(sort $(wildcard $(BR2_EXTERNAL_HASSOS_PATH)/package/*/*.mk))
+
+.PHONY: linux-check-dotconfig
+linux-check-dotconfig: linux-check-configuration-done
+	CC=$(TARGET_CC) LD=$(TARGET_LD) srctree=$(LINUX_SRCDIR) \
+	ARCH=$(if $(BR2_x86_64),x86,$(if $(BR2_arm)$(BR2_aarch64),arm,$(ARCH))) \
+	SRCARCH=$(if $(BR2_x86_64),x86,$(if $(BR2_arm)$(BR2_aarch64),arm,$(ARCH))) \
+	 $(BR2_EXTERNAL_HASSOS_PATH)/scripts/check-dotconfig.py \
+		$(BR2_CHECK_DOTCONFIG_OPTS) \
+		--src-kconfig $(LINUX_SRCDIR)Kconfig \
+		--actual-config $(LINUX_SRCDIR).config \
+		$(shell echo $(BR2_LINUX_KERNEL_CONFIG_FRAGMENT_FILES))

buildroot-external/scripts/check-dotconfig.py

@@ -0,0 +1,128 @@
+#!/usr/bin/env python
+
+import argparse
+from collections import namedtuple
+import re
+
+from kconfiglib import Kconfig
+
+
+# Can be either "CONFIG_OPTION=(y|m|n)" or "# CONFIG_OPTION is not set"
+regex = re.compile(
+    r"^(CONFIG_(?P<option_set>[A-Z0-9_]+)=(?P<value>[mny])"
+    r"|# CONFIG_(?P<option_unset>[A-Z0-9_]+) is not set)$"
+)
+
+# use namedtuple as a lightweight representation of fragment-defined options
+OptionValue = namedtuple("OptionValue", ["option", "value", "file", "line"])
+
+
+def parse_fragment(
+    filename: str, strip_path_prefix: str = None
+) -> dict[str, OptionValue]:
+    """
+    Parse Buildroot Kconfig fragment and return dict of OptionValue objects.
+    """
+    options: dict[str, OptionValue] = {}
+
+    with open(filename) as f:
+        if strip_path_prefix and filename.startswith(strip_path_prefix):
+            filename = filename[len(strip_path_prefix) :]
+
+        for line_number, line in enumerate(f, 1):
+            if matches := re.match(regex, line):
+                if matches["option_unset"]:
+                    value = OptionValue(
+                        matches["option_unset"], None, filename, line_number
+                    )
+                    options.update({matches.group("option_unset"): value})
+                else:
+                    value = OptionValue(
+                        matches["option_set"], matches["value"], filename, line_number
+                    )
+                    options.update({matches.group("option_set"): value})
+
+    return options
+
+
+def _format_message(
+    message: str, file: str, line: int, github_format: bool = False
+) -> str:
+    """
+    Format message with source file and line number.
+    """
+    if github_format:
+        return f"::warning file={file},line={line}::{message}"
+    return f"{message} (defined in {file}:{line})"
+
+
+def compare_configs(
+    expected_options: dict[str, OptionValue],
+    kconfig: Kconfig,
+    github_format: bool = False,
+) -> None:
+    """
+    Compare dictionary of expected options with actual Kconfig representation.
+    """
+    for option, spec in expected_options.items():
+        if option not in kconfig.syms:
+            print(
+                _format_message(
+                    f"{option}={spec.value} not found",
+                    file=spec.file,
+                    line=spec.line,
+                    github_format=github_format,
+                )
+            )
+        elif (val := kconfig.syms[option].str_value) != spec.value:
+            if spec.value is None and val == "n":
+                continue
+            print(
+                _format_message(
+                    f"{option}={spec.value} requested, actual = {val}",
+                    file=spec.file,
+                    line=spec.line,
+                    github_format=github_format,
+                )
+            )
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--src-kconfig", help="Path to top-level Kconfig file", required=True
+    )
+    parser.add_argument(
+        "--actual-config",
+        help="Path to config with actual config values (.config)",
+        required=True,
+    )
+    parser.add_argument(
+        "--github-format",
+        action="store_true",
+        help="Use Github Workflow commands output format",
+    )
+    parser.add_argument(
+        "-s",
+        "--strip-path-prefix",
+        help="Path prefix to strip in the output from config fragment paths",
+    )
+    parser.add_argument("fragments", nargs="+", help="Paths to source config fragments")
+
+    args = parser.parse_args()
+
+    expected_options: dict[str, OptionValue] = {}
+
+    for f in args.fragments:
+        expected_options.update(
+            parse_fragment(f, strip_path_prefix=args.strip_path_prefix)
+        )
+
+    kconfig = Kconfig(args.src_kconfig, warn_to_stderr=False)
+    kconfig.load_config(args.actual_config)
+
+    compare_configs(expected_options, kconfig, github_format=args.github_format)
+
+
+if __name__ == "__main__":
+    main()