Revert "checkpatch: remove and use clang-format instead"

The reverted commit intended to replace the old and no longer maintained
checkpatch with clang-format.

While I agree with this direction, the implementation was problematic.
The script was completely removed without providing an alternative,
leaving no verification for introduced code style. Additionally, the
clang-format configuration file that was added is not being used
anywhere. Furthermore, checkpatch performed two critical functions: it
verified both code quality and commit message format (including signoff
requirements). This second aspect was completely overlooked. As a
result, commits lacking proper signoff have already been merged.

Zephyr provides a better example of how this should be handled:
checkpatch was removed from GitHub workflows but remains available in
the repository for voluntary developer use. In parallel, CI enforces
coding style and commit quality through other dedicated tools.

This reverts commit aadcea2.

Signed-off-by: Tomasz Leman <tomasz.m.leman@intel.com>

Author: tmleman

.clang-format

@@ -1,7 +1,7 @@
 Read this section if there are some SPDX warnings above.
-Adding correct SPDX headers to new files can be tricky because:
+Pleasing checkpatch is hard when adding new files because:
 
-- a different SPDX style is expected for .c versus .h files.
+- checkpatch requests a different SPDX style for .c versus .h files.
   This is because some .h files are included in linker scripts or
   assembly code.
 - Some SOF reviewers reject C99 comments starting with //

.github/workflows/SPDX-README.md

@@ -0,0 +1,27 @@
+#!/bin/sh
+# SPDX-License-Identifier: BSD-3-Clause
+
+set -e
+
+# The purpose of this script is not to stop on the first checkpatch
+# failure and report at the end instead.
+#
+# Sample invocation:
+# $0 --codespell --strict < PR_SHAs.txt
+main()
+{
+    local failures=0
+    while read -r sha ; do
+        printf '\n    -------------- \n\n'
+        ./scripts/checkpatch.pl $@ -g $sha || failures=$((failures+1))
+    done
+    printf '\n    -------------- \n\n'
+
+    if [ $failures -ne 0 ]; then
+        cat .github/workflows/SPDX-README.md
+    fi
+
+    return $failures
+}
+
+main "$@"

.github/workflows/checkpatch_list.sh

@@ -18,6 +18,44 @@ permissions:
   contents: read
 
 jobs:
+  checkpatch:
+    runs-on: ubuntu-24.04
+
+    strategy:
+      fail-fast: false
+      matrix:
+        strictness: [null, --subjective]
+
+    env:
+      PR_NUM: ${{github.event.number}}
+      # TODO: reduce duplication with scripts/sof-*-commit-hook.sh
+      # thanks to either some .conf file or some wrapper script
+      CHK_CMD_OPTS: --ignore UNKNOWN_COMMIT_ID --codespell
+
+    steps:
+      # depth 2 so:
+      # ^1. we can show the Subject of the current target branch tip
+      # ^2. we reconnect/graft to the later fetch pull/1234/head,
+      - uses: actions/checkout@v4
+        with: {fetch-depth: 2}
+
+      - name: install codespell
+        run: sudo apt-get -y install codespell && dpkg -L codespell | grep dict
+
+      # See shallowness issue https://github.com/thesofproject/linux/issues/2556
+      - name: fetch PR commits
+        run: |
+           .github/workflows/shallowfetchPRcommits.sh \
+              ${GITHUB_REPOSITORY} "$PR_NUM"
+           # show what we got
+           git --no-pager log --oneline --graph --decorate --max-count=50
+
+      - name: checkpatch
+        env:
+          STRICTNESS: ${{ matrix.strictness }}
+        run: .github/workflows/checkpatch_list.sh ${CHK_CMD_OPTS}
+          ${STRICTNESS} < PR_SHAs.txt
+
   yamllint:
     runs-on: ubuntu-latest
     steps:

.github/workflows/codestyle.yml

@@ -49,6 +49,7 @@ tools/test/audio/reports/*
 tools/test/audio/zeros_in.raw
 
 __pycache__
+.checkpatch-camelcase.git.*
 
 build*/