tests: dt_binding_check: new test

We currently "rely" on Rob Herring's mail bot to provide sanity checking
on patches that touch device tree bindings:
https://lore.kernel.org/netdev/[email protected]

and that is sufficient in "public" settings (patches sent to
[email protected] and [email protected] also copied).

But in "private" settings (i.e. individual developers encouraged to do
sanity checking on their own, for example by running ingest_mdir), we
quickly find that Rob's mail bot is apparently closed source, and it has
happened more than once (at least to me) for me to miss newly introduced
dt_binding_check errors even if I did the due dilligence of running that
test locally. So an automated check would be good to have.

The justification for including it in NIPA is that while device tree
maintainers review binding patches, they get applied to the subsystem
tree (in this case netdev).

Furthermore, I don't see the overlap with Rob Herring's mail bot as
being a strong reason against such checks in NIPA, similar to how the
existence of Intel's kbuild test robot does not preclude NIPA from
having build tests.

In terms of implementation, "make dt_binding_check" does not always
nicely print "error" or "warning" on the lines with issues. Furthermore,
the errors are multi-line. So instead of filtering for error lines, here
we filter out the "normal" lines, which contain things such as "make",
"SCHEMA", "CHKDT", "LINT", "DTEX", "DTC" at the beginning.

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

Author: vladimiroltean

tests/patch/dt_binding_check/dt_binding_check.sh

@@ -0,0 +1,86 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright 2025 NXP
+
+HEAD=$(git rev-parse HEAD)
+ncpu=$(grep -c processor /proc/cpuinfo)
+rc=0
+
+pr() {
+    echo " ====== $* ======" | tee -a /dev/stderr
+}
+
+build() {
+    make -j $ncpu DT_CHECKER_FLAGS=-m dt_binding_check 2>&1
+}
+
+# Only run this check if the patch touches DT binding files.
+if ! git show --diff-filter=AM --pretty="" --name-only "${HEAD}" | \
+    grep -q -E "^Documentation/devicetree/bindings/"
+then
+    echo "No DT binding files touched, skip" >&"$DESC_FD"
+    exit 0
+fi
+
+# Create temporary files for logs
+tmpfile_o_raw=$(mktemp)
+tmpfile_n_raw=$(mktemp)
+tmpfile_o_filtered=$(mktemp)
+tmpfile_n_filtered=$(mktemp)
+tmp_new_issues=$(mktemp)
+
+echo "Tree base:"
+git log -1 --pretty='%h ("%s")' HEAD~
+echo "Now at:"
+git log -1 --pretty='%h ("%s")' HEAD
+
+# Define the filter pattern to exclude build noise from the make output.
+# We only want to see the actual error/warning lines.
+FILTER_PATTERN="^(make\[|  CHKDT|  DTC|  DTEX|  HOSTCC|  HOSTLD|  LEX|  LINT|  SCHEMA|  YACC|$)"
+
+pr "Checking before the patch"
+git checkout -q HEAD~
+
+# Run the check on the parent commit
+(build | tee -a "$tmpfile_o_raw") || true
+
+# Filter and sort the output to get only relevant issue lines
+grep -v -E "$FILTER_PATTERN" "$tmpfile_o_raw" | sort > "$tmpfile_o_filtered"
+incumbent_total=$(wc -l < "$tmpfile_o_filtered")
+
+pr "Checking the tree with the patch"
+git checkout -q "$HEAD"
+
+# Run the check on the new commit
+(build | tee -a "$tmpfile_n_raw") || true
+
+# Filter and sort the output
+grep -v -E "$FILTER_PATTERN" "$tmpfile_n_raw" | sort > "$tmpfile_n_filtered"
+current_total=$(wc -l < "$tmpfile_n_filtered")
+
+# Compare the filtered 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_filtered" "$tmpfile_n_filtered" | wc -l)
+
+# Use comm to find new issues (lines only in the new log, column 2)
+# and save them for later display.
+comm -13 "$tmpfile_o_filtered" "$tmpfile_n_filtered" > "$tmp_new_issues"
+new_issues_count=$(wc -l < "$tmp_new_issues")
+
+echo "Issues before: $incumbent_total, after: $current_total" \
+    "(Fixed: $fixed_issues_count, New: $new_issues_count)" >&"$DESC_FD"
+
+if [ "$new_issues_count" -gt 0 ]; then
+    echo "New issues added:" 1>&2
+    # Print the new issues we saved
+    cat "$tmp_new_issues" 1>&2
+    rc=1
+elif [ "$fixed_issues_count" -gt 0 ]; then
+    echo "Patch fixed $fixed_issues_count issue(s)." >&2
+    # No new issues, and some were fixed. This is a success.
+fi
+
+rm "$tmpfile_o_raw" "$tmpfile_n_raw" "$tmpfile_o_filtered" "$tmpfile_n_filtered" \
+    "$tmp_new_issues"
+
+exit $rc

tests/patch/dt_binding_check/info.json

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