linux-kernel - [PATCH v2 2/2] bitfield.h: split up __BF_FIELD

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Date:   Wed,  8 Jul 2020 16:04:02 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>, oss-drivers@...ronome.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jakub Kicinski <kuba@...nel.org>,
        Alex Elder <elder@...aro.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH v2 2/2] bitfield.h: split up __BF_FIELD_CHECK macro

This macro has a few expansion sites that pass literal 0s as parameters.
Split these up so that we do the precise checks where we care about
them.

Suggested-by: Alex Elder <elder@...aro.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
Changes V1-V2:
* New patch in v2.
* Rebased on 0001.

 .../netronome/nfp/nfpcore/nfp_nsp_eth.c       | 11 ++++----
 include/linux/bitfield.h                      | 26 +++++++++++++------
 2 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp_eth.c b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp_eth.c
index 311a5be25acb..938fc733fccb 100644
--- a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp_eth.c
+++ b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp_eth.c
@@ -492,11 +492,12 @@ nfp_eth_set_bit_config(struct nfp_nsp *nsp, unsigned int raw_idx,
 	return 0;
 }
 
-#define NFP_ETH_SET_BIT_CONFIG(nsp, raw_idx, mask, val, ctrl_bit)	\
-	({								\
-		__BF_FIELD_CHECK(mask, 0ULL, val, "NFP_ETH_SET_BIT_CONFIG: "); \
-		nfp_eth_set_bit_config(nsp, raw_idx, mask, __bf_shf(mask), \
-				       val, ctrl_bit);			\
+#define NFP_ETH_SET_BIT_CONFIG(nsp, raw_idx, mask, val, ctrl_bit)		\
+	({									\
+		__BF_FIELD_CHECK_MASK(mask, "NFP_ETH_SET_BIT_CONFIG: ");	\
+		__BF_FIELD_CHECK_VAL(mask, val, "NFP_ETH_SET_BIT_CONFIG: ");	\
+		nfp_eth_set_bit_config(nsp, raw_idx, mask, __bf_shf(mask),	\
+				       val, ctrl_bit);				\
 	})
 
 /**
diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
index 4e035aca6f7e..79651867beb3 100644
--- a/include/linux/bitfield.h
+++ b/include/linux/bitfield.h
@@ -41,18 +41,26 @@
 
 #define __bf_shf(x) (__builtin_ffsll(x) - 1)
 
-#define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx)			\
+#define __BF_FIELD_CHECK_MASK(_mask, _pfx)				\
 	({								\
 		BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask),		\
 				 _pfx "mask is not constant");		\
 		BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero");	\
+		__BUILD_BUG_ON_NOT_POWER_OF_2((_mask) +			\
+					      (1ULL << __bf_shf(_mask))); \
+	})
+
+#define __BF_FIELD_CHECK_VAL(_mask, _val, _pfx)				\
+	({								\
 		BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ?		\
 				 ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \
 				 _pfx "value too large for the field"); \
-		BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull,		\
+	})
+
+#define __BF_FIELD_CHECK_REG(_mask, _reg, _pfx)				\
+	({								\
+		BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ULL,		\
 				 _pfx "type of reg too small for mask"); \
-		__BUILD_BUG_ON_NOT_POWER_OF_2((_mask) +			\
-					      (1ULL << __bf_shf(_mask))); \
 	})
 
 /**
@@ -64,7 +72,7 @@
  */
 #define FIELD_MAX(_mask)						\
 	({								\
-		__BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: ");	\
+		__BF_FIELD_CHECK_MASK(_mask, "FIELD_MAX: ");		\
 		(typeof(_mask))((_mask) >> __bf_shf(_mask));		\
 	})
 
@@ -77,7 +85,7 @@
  */
 #define FIELD_FIT(_mask, _val)						\
 	({								\
-		__BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: ");	\
+		__BF_FIELD_CHECK_MASK(_mask, "FIELD_FIT: ");		\
 		!((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
 	})
 
@@ -91,7 +99,8 @@
  */
 #define FIELD_PREP(_mask, _val)						\
 	({								\
-		__BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: ");	\
+		__BF_FIELD_CHECK_MASK(_mask, "FIELD_PREP: ");		\
+		__BF_FIELD_CHECK_VAL(_mask, _val, "FIELD_PREP: ");	\
 		((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask);	\
 	})
 
@@ -105,7 +114,8 @@
  */
 #define FIELD_GET(_mask, _reg)						\
 	({								\
-		__BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: ");	\
+		__BF_FIELD_CHECK_MASK(_mask, "FIELD_GET: ");		\
+		__BF_FIELD_CHECK_REG(_mask, _reg,  "FIELD_GET: ");	\
 		(typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask));	\
 	})
 
-- 
2.27.0.383.g050319c2ae-goog