[PATCH v4 1/5] coccinelle: misc: Add field_modify script

[Luo Jie]

Find and suggest conversions of opencoded field modify patterns with
the wrapper FIELD_MODIFY() API defined in include/linux/bitfield.h
for catching the possible parameter type error in the compile time.

Signed-off-by: Luo Jie <quic_luoj at quicinc.com>
---
 scripts/coccinelle/misc/field_modify.cocci | 61 ++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/scripts/coccinelle/misc/field_modify.cocci b/scripts/coccinelle/misc/field_modify.cocci
new file mode 100644
index 000000000000..48b00194a265
--- /dev/null
+++ b/scripts/coccinelle/misc/field_modify.cocci
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/// Replace below code with the wrapper FIELD_MODIFY(MASK, &reg, val)
+/// - reg &= ~MASK;
+/// - reg |= FIELD_PREP(MASK, val);
+//
+// Confidence: High
+// Author: Luo Jie <quic_luoj at quicinc.com>
+// Copyright: (C) 2025 Qualcomm Innovation Center, Inc.
+// Keywords: FIELD_PREP, FIELD_MODIFY
+// Options: --include-headers
+
+virtual context
+virtual patch
+virtual org
+virtual report
+
+@ depends on context && !patch && !org && !report@
+identifier reg, val;
+constant mask;
+symbol FIELD_PREP;
+@@
+
+* reg &= ~mask;
+* reg |= FIELD_PREP(mask, val);
+
+@ depends on !context && patch && !org && !report @
+identifier reg, val;
+constant mask;
+symbol FIELD_PREP, FIELD_MODIFY;
+@@
+
+-reg &= ~mask;
+-reg |= FIELD_PREP(mask, val);
++FIELD_MODIFY(mask, &reg, val);
+
+ at r depends on !context && !patch && (org || report)@
+identifier reg, val;
+constant mask;
+symbol FIELD_PREP;
+position p;
+@@
+
+ reg &= ~mask;
+ reg |= FIELD_PREP at p(mask, val);
+
+ at script:python depends on report@
+p << r.p;
+x << r.reg;
+@@
+
+msg="WARNING: Consider using FIELD_MODIFY helper on %s" % (x)
+coccilib.report.print_report(p[0], msg)
+
+ at script:python depends on org@
+p << r.p;
+x << r.reg;
+@@
+
+msg="WARNING: Consider using FIELD_MODIFY helper on %s" % (x)
+msg_safe=msg.replace("[","@(").replace("]",")")
+coccilib.org.print_todo(p[0], msg_safe)

-- 
2.34.1