From: Xining Xu <mac.xxn@outlook.com>

If function-like macros do not utilize a parameter, it might result in a
build warning.  In our coding style guidelines, we advocate for utilizing
static inline functions to replace such macros.  This patch verifies
compliance with the new rule.

For a macro such as the one below,

 #define test(a) do { } while (0)

The test result is as follows.

 ERROR: Parameter 'a' is not used in function-like macro, please use static
 inline instead
 #21: FILE: mm/init-mm.c:20:
 +#define test(a) do { } while (0)

 total: 1 errors, 0 warnings, 8 lines checked

Signed-off-by: Xining Xu <mac.xxn@outlook.com>
Tested-by: Barry Song <v-songbaohua@oppo.com>
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Huacai Chen <chenhuacai@loongson.cn>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Mark Brown <broonie@kernel.org>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Dwaipayan Ray <dwaipayanray1@gmail.com>
Cc: Joe Perches <joe@perches.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Jeff Johnson <quic_jjohnson@quicinc.com>
Cc: Charlemagne Lasse <charlemagnelasse@gmail.com>
---
 scripts/checkpatch.pl | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 9c4c4a61bc83..9895d7e38a9f 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6040,6 +6040,12 @@ sub process {
 					CHK("MACRO_ARG_PRECEDENCE",
 					    "Macro argument '$arg' may be better as '($arg)' to avoid precedence issues\n" . "$herectx");
 				}
+
+# check if this is an unused argument
+				if ($define_stmt !~ /\b$arg\b/) {
+					WARN("MACRO_ARG_UNUSED",
+						"Argument '$arg' is not used in function-like macro\n" . "$herectx");
+				}
 			}
 
 # check for macros with flow control, but without ## concatenation
-- 
2.34.1

On Mon, 2024-04-01 at 14:21 +1300, Barry Song wrote:
> From: Xining Xu <mac.xxn@outlook.com>
> 
> If function-like macros do not utilize a parameter, it might result in a
> build warning.  In our coding style guidelines, we advocate for utilizing
> static inline functions to replace such macros.  This patch verifies
> compliance with the new rule.
> 
> For a macro such as the one below,
> 
>  #define test(a) do { } while (0)
> 
> The test result is as follows.
> 
>  ERROR: Parameter 'a' is not used in function-like macro, please use static
>  inline instead
>  #21: FILE: mm/init-mm.c:20:
>  +#define test(a) do { } while (0)

This is no longer true.
Please update the ERROR->WARN and message as below

Ideally, this would have an update to
Documentation/dev-tools/checkpatch.rst

to describe the new --verbose message type

> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -6040,6 +6040,12 @@ sub process {
>  					CHK("MACRO_ARG_PRECEDENCE",
>  					    "Macro argument '$arg' may be better as '($arg)' to avoid precedence issues\n" . "$herectx");
>  				}
> +
> +# check if this is an unused argument
> +				if ($define_stmt !~ /\b$arg\b/) {
> +					WARN("MACRO_ARG_UNUSED",
> +						"Argument '$arg' is not used in function-like macro\n" . "$herectx");
> +				}