tests: dtbs_check: new test

The idea is that subsystems (i.e. netdev) apply dt-binding patches,
but those can introduce warnings in existing device trees. So we need
a check.

The trouble is that NIPA builds only for the host architecture (x86_64)
whereas device trees are for lots of other architectures.

The kernel build technically requires a cross-compilation toolchain, but
"make dtbs" technically doesn't cross-compile anything. We just need the
C preprocessor (gcc -E).

This is a bit of a hack, but to get each and every architecture to
compile, we use exclusively the host gcc and set up arch-specific
'shims' for it (which disregard options that the host gcc doesn't
understand).

Signed-off-by: Vladimir Oltean <[email protected]>

Author: vladimiroltean

tests/patch/dtbs_check/dtbs_check.sh

@@ -0,0 +1,185 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright 2025-2026 NXP
+
+HEAD=$(git rev-parse HEAD)
+nproc=$(grep -c processor /proc/cpuinfo)
+build_flags="-j $nproc"
+rc=0
+
+architectures=(
+    "arc" \
+    "arm" \
+    "arm64" \
+    "csky" \
+    "loongarch" \
+    "microblaze" \
+    "mips" \
+    "nios2" \
+    "openrisc" \
+    "powerpc" \
+    "riscv" \
+    "sh" \
+    "xtensa" \
+)
+
+pr() {
+    echo " ====== $* ======" | tee -a /dev/stderr
+}
+
+# "make dtbs" will fail on many archs during the syncconfig stage, where it
+# tries to probe the cross-compiler version. We don't actually need any
+# cross-compilation feature, the host gcc could in principle handle everything
+# as long as we filter out arch-specific flags.
+setup_shims() {
+    local shims_dir="$1"
+
+    mkdir -p "$shims_dir"
+
+    cat > "$shims_dir/gcc" << 'EOF'
+#!/bin/bash
+args=()
+skip_next=false
+for arg in "$@"; do
+  if [[ "$skip_next" == "true" ]]; then
+    skip_next=false
+    continue
+  fi
+  case "$arg" in
+    -mdiv|-mno-stack-size|-mhard-float|-msoft-float|-mcpu=*|-march=*|-mtune=*|\
+    -mmedium-calls|-mlock|-mswape|-munaligned-access|-mno-sdata|-mbig-endian|\
+    -mabi=*|-mcmodel=*|-G|-mno-abicalls|-EB|0)
+      ;;
+    *)
+      args+=("$arg")
+      ;;
+  esac
+done
+exec /usr/bin/gcc "${args[@]}"
+EOF
+
+    chmod +x "$shims_dir/gcc"
+
+    # Special case for xtensa
+    ln -s $(which gcc) "$shims_dir/xtensa_fsf-gcc"
+    ln -s "$(which ld)" "$shims_dir/xtensa_fsf-ld"
+}
+
+prep_config() {
+    local arch=$1
+    local output_dir=$2
+    local shims_dir=$3
+    PATH="$shims_dir:$PATH" make ARCH=$arch O=$output_dir allmodconfig $build_flags
+}
+
+build() {
+    local arch=$1
+    local output_dir=$2
+    local shims_dir=$3
+    PATH="$shims_dir:$PATH" make -s ARCH=$arch O=$output_dir $build_flags DT_CHECKER_FLAGS=-m CHECK_DT_BINDING=y dtbs 2>&1
+}
+
+clean_build() {
+    local output_dir=$1
+    rm -rf "$output_dir"
+}
+
+schema_modified=false
+if git show --diff-filter=AM --pretty="" --name-only "${HEAD}" | \
+    grep -q -E "^Documentation/devicetree/bindings/"
+then
+    schema_modified=true
+fi
+
+touched_archs=()
+for arch in "${architectures[@]}"; do
+    if git show --diff-filter=AM --pretty="" --name-only "${HEAD}" | \
+        grep -q -E "^arch/${arch}/boot/dts/"
+    then
+        touched_archs+=("$arch")
+    fi
+done
+
+test_archs=()
+if [ "$schema_modified" = true ]; then
+    test_archs=("${architectures[@]}")
+    echo "DT schema files modified, testing all architectures" >&"$DESC_FD"
+elif [ ${#touched_archs[@]} -gt 0 ]; then
+    test_archs=("${touched_archs[@]}")
+    echo "DTS files touched for architectures: ${test_archs[*]}" >&"$DESC_FD"
+else
+    echo "No DT schema or DTS files touched, skip" >&"$DESC_FD"
+    exit 0
+fi
+
+echo "Tree base:"
+git log -1 --pretty='%h ("%s")' HEAD~
+echo "Now at:"
+git log -1 --pretty='%h ("%s")' HEAD
+
+# Set up compiler shims
+shims_dir="$PWD/shims"
+setup_shims "$shims_dir"
+
+for arch in "${test_archs[@]}"; do
+    output_dir="build_dtbs_check_${arch}/"
+
+    tmpfile_o_raw=$(mktemp)
+    tmpfile_n_raw=$(mktemp)
+    tmp_new_issues=$(mktemp)
+
+    pr "Checking $arch before the patch"
+    git checkout -q HEAD~
+
+    # Prepare config and run the check on the parent commit
+    clean_build "$output_dir"
+    prep_config "$arch" "$output_dir" "$shims_dir"
+    (build "$arch" "$output_dir" "$shims_dir" | tee -a "$tmpfile_o_raw") || true
+
+    # Sort the output
+    sort "$tmpfile_o_raw" > "${tmpfile_o_raw}.sorted"
+    mv "${tmpfile_o_raw}.sorted" "$tmpfile_o_raw"
+    incumbent_total=$(wc -l < "$tmpfile_o_raw")
+
+    pr "Checking $arch with the patch"
+    git checkout -q "$HEAD"
+
+    # Prepare config and run the check on the new commit
+    clean_build "$output_dir"
+    prep_config "$arch" "$output_dir" "$shims_dir"
+    (build "$arch" "$output_dir" "$shims_dir" | tee -a "$tmpfile_n_raw") || true
+
+    # Sort the output
+    sort "$tmpfile_n_raw" > "${tmpfile_n_raw}.sorted"
+    mv "${tmpfile_n_raw}.sorted" "$tmpfile_n_raw"
+    current_total=$(wc -l < "$tmpfile_n_raw")
+
+    # Compare the lists to find new and fixed issues
+    # Use comm to find fixed issues (lines only in the old log, column 1).
+    fixed_issues_count=$(comm -23 "$tmpfile_o_raw" "$tmpfile_n_raw" | wc -l)
+
+    # Use comm to find new issues (lines only in the new log, column 2)
+    # and save them for later display.
+    comm -13 "$tmpfile_o_raw" "$tmpfile_n_raw" > "$tmp_new_issues"
+    new_issues_count=$(wc -l < "$tmp_new_issues")
+
+    echo "[$arch] Issues before: $incumbent_total, after: $current_total" \
+        "(Fixed: $fixed_issues_count, New: $new_issues_count)" >&"$DESC_FD"
+
+    if [ "$new_issues_count" -gt 0 ]; then
+        echo "[$arch] New issues added:" 1>&2
+        # Print the new issues we saved
+        cat "$tmp_new_issues" 1>&2
+        rc=1
+    elif [ "$fixed_issues_count" -gt 0 ]; then
+        echo "[$arch] Patch fixed $fixed_issues_count issue(s)." >&2
+        # No new issues, and some were fixed. This is a success.
+    fi
+
+    rm "$tmpfile_o_raw" "$tmpfile_n_raw" "$tmp_new_issues"
+done
+
+# Clean up shims directory
+rm -rf "$shims_dir"
+
+exit $rc

tests/patch/dtbs_check/info.json

@@ -0,0 +1,3 @@
+{
+  "run": ["dtbs_check.sh"]
+}