[PATCH v5] scripts: checkpatch: move Rust-specific lints to separate file

[Jason Hall <jason.kei.hall@gmail.com>]

Move Rust linting logic into scripts/rust_checkpatch.pl to prevent
further growth of the main checkpatch.pl script.

Warn against the use of .unwrap() and .expect() unless accompanied by
a '// PANIC:' comment. This enforces safety standards in the Rust-
for-Linux project until upstream Clippy lints are integrated.

Suggested-by: Joe Perches <joe@perches.com>
Suggested-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://github.com/Rust-for-linux/linux/issues/1191
Signed-off-by: Jason Hall <jason.kei.hall@gmail.com>

---
v5:
 - Move Rust-specific logic to scripts/rust_checkpatch.pl (Suggested by Joe Perches).
 - Add conditional loading hook in scripts/checkpatch.pl.
 - Updated regex to use house-style comments.
v4:
 - Use imperative mood in commit description.
 - Fix patch formatting and placement of '---' separator.
v3:
 - Use non-capturing groups (?:) to optimize regex.
v2:
 - Switch from \b to (\.|::) to avoid false positives in strings.
 - Add : to PANIC comment check.
---
 scripts/checkpatch.pl      | 14 ++++++++++++++
 scripts/rust_checkpatch.pl | 25 +++++++++++++++++++++++++
 2 files changed, 39 insertions(+)
 create mode 100644 scripts/rust_checkpatch.pl

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index c0250244cf7a..f75cb70ad0dd 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -20,6 +20,12 @@ my $D = dirname(abs_path($P));
 
 my $V = '0.32';
 
+my $rust_checkpatch_available = 0;
+if (-e "$D/rust_checkpatch.pl") {
+	require "$D/rust_checkpatch.pl";
+	$rust_checkpatch_available = 1;
+}
+
 use Getopt::Long qw(:config no_auto_abbrev);
 
 my $quiet = 0;
@@ -2947,6 +2953,14 @@ sub process {
 
 		$cnt_lines++ if ($realcnt != 0);
 
+# Check for Rust-specific lints
+		if ($rust_checkpatch_available && $realfile =~ /\.rs$/) {
+			my ($type, $msg) = process_rust($line, $rawline, $herecurr);
+			if ($type) {
+				WARN($type, $msg);
+			}
+		}
+
 # Verify the existence of a commit log if appropriate
 # 2 is used because a $signature is counted in $commit_log_lines
 		if ($in_commit_log) {
diff --git a/scripts/rust_checkpatch.pl b/scripts/rust_checkpatch.pl
new file mode 100644
index 000000000000..69db5ded7371
--- /dev/null
+++ b/scripts/rust_checkpatch.pl
@@ -0,0 +1,25 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0
+#
+# (c) 2026, Jason K. Hall <jason.kei.hall@gmail.com>
+
+use strict;
+use warnings;
+
+sub process_rust {
+    my ($line, $rawline, $herecurr) = @_;
+
+    # check for Rust unwrap/expect
+    if ($line =~ /^\+/) {
+        if ($line =~ /(?:\.|::)(?:unwrap|expect)\s*\(/ &&
+            $rawline !~ /\/\/\s*PANIC:/ &&
+            $line !~ /^\+\s*\/\// &&
+            $line !~ /^\+\s*assert/) {
+            return ("RUST_UNWRAP",
+                    "Avoid unwrap() or expect() in Rust code; use proper error handling (Result) or justify with a '// PANIC: ...' comment.\n" . $herecurr);
+        }
+    }
+    return ();
+}
+
+1;
\ No newline at end of file
-- 
2.43.0