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Date:   Wed, 29 Sep 2021 12:44:16 +0300
From:   Ido Schimmel <idosch@nvidia.com>
To:     kernel test robot <lkp@intel.com>, <nathan@kernel.org>
CC:     "llvm@lists.linux.dev" <llvm@lists.linux.dev>,
        "kbuild-all@lists.01.org" <kbuild-all@lists.01.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Jiri Pirko <jiri@nvidia.com>
Subject: Re:
 drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_actions.c:2022:1: warning:
 unused function 'mlxsw_afa_sampler_mirror_agent_get'
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References: <202109290245.bpgij5Zs-lkp@intel.com>
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On Tue, Sep 28, 2021 at 09:06:54PM +0300, kernel test robot wrote:
> All warnings (new ones prefixed by >>):
> 
>    static inline u32 mlxsw_##_type##_##_cname##_##_iname##_get(const char ^
>    <scratch space>:119:1: note: expanded from here
>    mlxsw_afa_polcnt_c_p_get
>    ^

Nathan,

I saw your reply to a similar issue here [1] and I got the impression
that you are leading the LLVM-related efforts, so I thought I will
consult with you regarding a possible solution.

The inline functions that clang is complaining about are generated by
macros that make it easy to set/get fields in the payloads of
configuration messages used to communicate with the device. It is
possible that sometime we only set a field, but never retrieve its value
such as in the warning above. This is very much intentional and not
indicative of a function we forgot to remove.

The patch below [2] adds the "__maybe_unused" keyword to these macros
and makes clang happy [3].

Is this acceptable or you suggest a different solution?

Thanks

[1] https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org/thread/TIUWC7KZVTHGJKIZ4M3LI3JJYVAAINJX/

[2]
diff --git a/drivers/net/ethernet/mellanox/mlxsw/item.h b/drivers/net/ethernet/mellanox/mlxsw/item.h
index e92cadc98128..d2c8f436efb7 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/item.h
+++ b/drivers/net/ethernet/mellanox/mlxsw/item.h
@@ -290,13 +290,13 @@ static struct mlxsw_item __ITEM_NAME(_type, _cname, _iname) = {			\
 	.size = {.bits = _sizebits,},						\
 	.name = #_type "_" #_cname "_" #_iname,					\
 };										\
-static inline u8								\
+static inline u8 __maybe_unused							\
 mlxsw_##_type##_##_cname##_##_iname##_get(const char *buf, unsigned short index)\
 {										\
 	return __mlxsw_item_get8(buf, &__ITEM_NAME(_type, _cname, _iname),	\
 				 index);					\
 }										\
-static inline void								\
+static inline void __maybe_unused						\
 mlxsw_##_type##_##_cname##_##_iname##_set(char *buf, unsigned short index,	\
 					  u8 val)				\
 {										\
@@ -311,11 +311,13 @@ static struct mlxsw_item __ITEM_NAME(_type, _cname, _iname) = {			\
 	.size = {.bits = _sizebits,},						\
 	.name = #_type "_" #_cname "_" #_iname,					\
 };										\
-static inline u16 mlxsw_##_type##_##_cname##_##_iname##_get(const char *buf)	\
+static inline u16 __maybe_unused						\
+mlxsw_##_type##_##_cname##_##_iname##_get(const char *buf)			\
 {										\
 	return __mlxsw_item_get16(buf, &__ITEM_NAME(_type, _cname, _iname), 0);	\
 }										\
-static inline void mlxsw_##_type##_##_cname##_##_iname##_set(char *buf, u16 val)\
+static inline void __maybe_unused						\
+mlxsw_##_type##_##_cname##_##_iname##_set(char *buf, u16 val)			\
 {										\
 	__mlxsw_item_set16(buf, &__ITEM_NAME(_type, _cname, _iname), 0, val);	\
 }
@@ -331,13 +333,13 @@ static struct mlxsw_item __ITEM_NAME(_type, _cname, _iname) = {			\
 	.size = {.bits = _sizebits,},						\
 	.name = #_type "_" #_cname "_" #_iname,					\
 };										\
-static inline u16								\
+static inline u16 __maybe_unused						\
 mlxsw_##_type##_##_cname##_##_iname##_get(const char *buf, unsigned short index)\
 {										\
 	return __mlxsw_item_get16(buf, &__ITEM_NAME(_type, _cname, _iname),	\
 				  index);					\
 }										\
-static inline void								\
+static inline void __maybe_unused						\
 mlxsw_##_type##_##_cname##_##_iname##_set(char *buf, unsigned short index,	\
 					  u16 val)				\
 {										\
@@ -352,11 +354,13 @@ static struct mlxsw_item __ITEM_NAME(_type, _cname, _iname) = {			\
 	.size = {.bits = _sizebits,},						\
 	.name = #_type "_" #_cname "_" #_iname,					\
 };										\
-static inline u32 mlxsw_##_type##_##_cname##_##_iname##_get(const char *buf)	\
+static inline u32 __maybe_unused						\
+mlxsw_##_type##_##_cname##_##_iname##_get(const char *buf)			\
 {										\
 	return __mlxsw_item_get32(buf, &__ITEM_NAME(_type, _cname, _iname), 0);	\
 }										\
-static inline void mlxsw_##_type##_##_cname##_##_iname##_set(char *buf, u32 val)\
+static inline void __maybe_unused						\
+mlxsw_##_type##_##_cname##_##_iname##_set(char *buf, u32 val)			\
 {										\
 	__mlxsw_item_set32(buf, &__ITEM_NAME(_type, _cname, _iname), 0, val);	\
 }
@@ -372,13 +376,13 @@ static struct mlxsw_item __ITEM_NAME(_type, _cname, _iname) = {			\
 	.size = {.bits = _sizebits,},						\
 	.name = #_type "_" #_cname "_" #_iname,					\
 };										\
-static inline u32								\
+static inline u32 __maybe_unused						\
 mlxsw_##_type##_##_cname##_##_iname##_get(const char *buf, unsigned short index)\
 {										\
 	return __mlxsw_item_get32(buf, &__ITEM_NAME(_type, _cname, _iname),	\
 				  index);					\
 }										\
-static inline void								\
+static inline void __maybe_unused						\
 mlxsw_##_type##_##_cname##_##_iname##_set(char *buf, unsigned short index,	\
 					  u32 val)				\
 {										\
@@ -393,11 +397,13 @@ static struct mlxsw_item __ITEM_NAME(_type, _cname, _iname) = {			\
 	.size = {.bits = _sizebits,},						\
 	.name = #_type "_" #_cname "_" #_iname,					\
 };										\
-static inline u64 mlxsw_##_type##_##_cname##_##_iname##_get(const char *buf)	\
+static inline u64 __maybe_unused						\
+mlxsw_##_type##_##_cname##_##_iname##_get(const char *buf)			\
 {										\
 	return __mlxsw_item_get64(buf, &__ITEM_NAME(_type, _cname, _iname), 0);	\
 }										\
-static inline void mlxsw_##_type##_##_cname##_##_iname##_set(char *buf, u64 val)\
+static inline void __maybe_unused						\
+mlxsw_##_type##_##_cname##_##_iname##_set(char *buf, u64 val)			\
 {										\
 	__mlxsw_item_set64(buf, &__ITEM_NAME(_type, _cname, _iname), 0,	val);	\
 }
@@ -413,13 +419,13 @@ static struct mlxsw_item __ITEM_NAME(_type, _cname, _iname) = {			\
 	.size = {.bits = _sizebits,},						\
 	.name = #_type "_" #_cname "_" #_iname,					\
 };										\
-static inline u64								\
+static inline u64 __maybe_unused						\
 mlxsw_##_type##_##_cname##_##_iname##_get(const char *buf, unsigned short index)\
 {										\
 	return __mlxsw_item_get64(buf, &__ITEM_NAME(_type, _cname, _iname),	\
 				  index);					\
 }										\
-static inline void								\
+static inline void __maybe_unused						\
 mlxsw_##_type##_##_cname##_##_iname##_set(char *buf, unsigned short index,	\
 					  u64 val)				\
 {										\
@@ -433,19 +439,19 @@ static struct mlxsw_item __ITEM_NAME(_type, _cname, _iname) = {			\
 	.size = {.bytes = _sizebytes,},						\
 	.name = #_type "_" #_cname "_" #_iname,					\
 };										\
-static inline void								\
+static inline void __maybe_unused						\
 mlxsw_##_type##_##_cname##_##_iname##_memcpy_from(const char *buf, char *dst)	\
 {										\
 	__mlxsw_item_memcpy_from(buf, dst,					\
 				 &__ITEM_NAME(_type, _cname, _iname), 0);	\
 }										\
-static inline void								\
+static inline void __maybe_unused						\
 mlxsw_##_type##_##_cname##_##_iname##_memcpy_to(char *buf, const char *src)	\
 {										\
 	__mlxsw_item_memcpy_to(buf, src,					\
 			       &__ITEM_NAME(_type, _cname, _iname), 0);		\
 }										\
-static inline char *								\
+static inline char * __maybe_unused						\
 mlxsw_##_type##_##_cname##_##_iname##_data(char *buf)				\
 {										\
 	return __mlxsw_item_data(buf, &__ITEM_NAME(_type, _cname, _iname), 0);	\
@@ -460,7 +466,7 @@ static struct mlxsw_item __ITEM_NAME(_type, _cname, _iname) = {			\
 	.size = {.bytes = _sizebytes,},						\
 	.name = #_type "_" #_cname "_" #_iname,					\
 };										\
-static inline void								\
+static inline void __maybe_unused						\
 mlxsw_##_type##_##_cname##_##_iname##_memcpy_from(const char *buf,		\
 						  unsigned short index,		\
 						  char *dst)			\
@@ -468,7 +474,7 @@ mlxsw_##_type##_##_cname##_##_iname##_memcpy_from(const char *buf,		\
 	__mlxsw_item_memcpy_from(buf, dst,					\
 				 &__ITEM_NAME(_type, _cname, _iname), index);	\
 }										\
-static inline void								\
+static inline void __maybe_unused						\
 mlxsw_##_type##_##_cname##_##_iname##_memcpy_to(char *buf,			\
 						unsigned short index,		\
 						const char *src)		\
@@ -476,7 +482,7 @@ mlxsw_##_type##_##_cname##_##_iname##_memcpy_to(char *buf,			\
 	__mlxsw_item_memcpy_to(buf, src,					\
 			       &__ITEM_NAME(_type, _cname, _iname), index);	\
 }										\
-static inline char *								\
+static inline char * __maybe_unused						\
 mlxsw_##_type##_##_cname##_##_iname##_data(char *buf, unsigned short index)	\
 {										\
 	return __mlxsw_item_data(buf,						\
@@ -491,14 +497,14 @@ static struct mlxsw_item __ITEM_NAME(_type, _cname, _iname) = {			\
 	.size = {.bytes = _sizebytes,},						\
 	.name = #_type "_" #_cname "_" #_iname,					\
 };										\
-static inline u8								\
+static inline u8 __maybe_unused							\
 mlxsw_##_type##_##_cname##_##_iname##_get(const char *buf, u16 index)		\
 {										\
 	return __mlxsw_item_bit_array_get(buf,					\
 					  &__ITEM_NAME(_type, _cname, _iname),	\
 					  index);				\
 }										\
-static inline void								\
+static inline void __maybe_unused						\
 mlxsw_##_type##_##_cname##_##_iname##_set(char *buf, u16 index, u8 val)		\
 {										\
 	return __mlxsw_item_bit_array_set(buf,					\

[3]
$ make -j8 CC=clang C=2 W=1 drivers/net/ethernet/mellanox/mlxsw/                                                                                      
  DESCEND bpf/resolve_btfids                                                          
  DESCEND objtool                                                                     
  CHECK   scripts/mod/empty.c                                                         
  CALL    scripts/atomic/check-atomics.sh                                             
  CALL    scripts/checksyscalls.sh                                                    
  CHECK   drivers/net/ethernet/mellanox/mlxsw/core.c              
  CHECK   drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_keys.c       
  CHECK   drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_actions.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/core_env.c     
  CHECK   drivers/net/ethernet/mellanox/mlxsw/core_hwmon.c       
  CHECK   drivers/net/ethernet/mellanox/mlxsw/core_thermal.c   
  CHECK   drivers/net/ethernet/mellanox/mlxsw/pci.c         
  CHECK   drivers/net/ethernet/mellanox/mlxsw/i2c.c         
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum.c     
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_buffers.c         
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_switchdev.c    
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c  
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_router_xm.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum1_kvdl.c  
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum2_kvdl.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c 
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_ctcam.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_atcam.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_erp.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum1_acl_tcam.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum2_acl_tcam.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_bloom_filter.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_acl.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_flow.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_matchall.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_flower.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_cnt.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_ipip.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_flex_actions.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_flex_keys.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum1_mr_tcam.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum2_mr_tcam.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_mr_tcam.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_mr.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_qdisc.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_nve.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_nve_vxlan.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_dpipe.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_trap.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_ethtool.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_policer.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_dcb.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/spectrum_ptp.c
  CHECK   drivers/net/ethernet/mellanox/mlxsw/minimal.c