X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;f=drivers%2Fnet%2Fsfc%2Fbase%2Fefx_types.h;h=65168ab79a23cfe2c019c7861c7a1acd1c952e70;hb=2db818aa86a7649259a548711a5ce1e1edbe11ef;hp=0581f67f44b352576789a13d1f0d381fed3af55a;hpb=ca33590b6af032bff57d9cc70455660466a654b2;p=deb_dpdk.git

diff --git a/drivers/net/sfc/base/efx_types.h b/drivers/net/sfc/base/efx_types.h
index 0581f67f..65168ab7 100644
--- a/drivers/net/sfc/base/efx_types.h
+++ b/drivers/net/sfc/base/efx_types.h
@@ -328,6 +328,16 @@ extern int fix_lint;
 #define	FIX_LINT(_x)	(_x)
 #endif
 
+/*
+ * Saturation arithmetic subtract with minimum equal to zero.
+ *
+ * Use saturating arithmetic to ensure a non-negative result. This
+ * avoids undefined behaviour (and compiler warnings) when used as a
+ * shift count.
+ */
+#define	EFX_SSUB(_val, _sub) \
+	((_val) > (_sub) ? ((_val) - (_sub)) : 0)
+
 /*
  * Extract bit field portion [low,high) from the native-endian element
  * which contains bits [min,max).
@@ -347,8 +357,8 @@ extern int fix_lint;
 	((FIX_LINT(_low > _max) || FIX_LINT(_high < _min)) ?		\
 		0U :							\
 		((_low > _min) ?					\
-			((_element) >> (_low - _min)) :			\
-			((_element) << (_min - _low))))
+			((_element) >> EFX_SSUB(_low, _min)) :		\
+			((_element) << EFX_SSUB(_min, _low))))
 
 /*
  * Extract bit field portion [low,high) from the 64-bit little-endian
@@ -537,29 +547,29 @@ extern int fix_lint;
 	(((_low > _max) || (_high < _min)) ?				\
 		0U :							\
 		((_low > _min) ?					\
-			(((uint64_t)(_value)) << (_low - _min)) :	\
-			(((uint64_t)(_value)) >> (_min - _low))))
+			(((uint64_t)(_value)) << EFX_SSUB(_low, _min)) :\
+			(((uint64_t)(_value)) >> EFX_SSUB(_min, _low))))
 
 #define	EFX_INSERT_NATIVE32(_min, _max, _low, _high, _value)		\
 	(((_low > _max) || (_high < _min)) ?				\
 		0U :							\
 		((_low > _min) ?					\
-			(((uint32_t)(_value)) << (_low - _min)) :	\
-			(((uint32_t)(_value)) >> (_min - _low))))
+			(((uint32_t)(_value)) << EFX_SSUB(_low, _min)) :\
+			(((uint32_t)(_value)) >> EFX_SSUB(_min, _low))))
 
 #define	EFX_INSERT_NATIVE16(_min, _max, _low, _high, _value)		\
 	(((_low > _max) || (_high < _min)) ?				\
 		0U :							\
 		(uint16_t)((_low > _min) ?				\
-				((_value) << (_low - _min)) :		\
-				((_value) >> (_min - _low))))
+				((_value) << EFX_SSUB(_low, _min)) :	\
+				((_value) >> EFX_SSUB(_min, _low))))
 
 #define	EFX_INSERT_NATIVE8(_min, _max, _low, _high, _value)		\
 	(((_low > _max) || (_high < _min)) ?				\
 		0U :							\
 		(uint8_t)((_low > _min) ?				\
-				((_value) << (_low - _min)) :	\
-				((_value) >> (_min - _low))))
+				((_value) << EFX_SSUB(_low, _min)) :	\
+				((_value) >> EFX_SSUB(_min, _low))))
 
 /*
  * Construct bit field portion
@@ -1288,22 +1298,22 @@ extern int fix_lint;
 
 #define	EFX_SHIFT64(_bit, _base)					\
 	(((_bit) >= (_base) && (_bit) < (_base) + 64) ?			\
-		((uint64_t)1 << ((_bit) - (_base))) :			\
+		((uint64_t)1 << EFX_SSUB((_bit), (_base))) :		\
 		0U)
 
 #define	EFX_SHIFT32(_bit, _base)					\
 	(((_bit) >= (_base) && (_bit) < (_base) + 32) ?			\
-		((uint32_t)1 << ((_bit) - (_base))) :			\
+		((uint32_t)1 << EFX_SSUB((_bit),(_base))) :		\
 		0U)
 
 #define	EFX_SHIFT16(_bit, _base)					\
 	(((_bit) >= (_base) && (_bit) < (_base) + 16) ?			\
-		(uint16_t)(1 << ((_bit) - (_base))) :			\
+		(uint16_t)(1 << EFX_SSUB((_bit), (_base))) :		\
 		0U)
 
 #define	EFX_SHIFT8(_bit, _base)						\
 	(((_bit) >= (_base) && (_bit) < (_base) + 8) ?			\
-		(uint8_t)(1 << ((_bit) - (_base))) :			\
+		(uint8_t)(1 << EFX_SSUB((_bit), (_base))) :		\
 		0U)
 
 #define	EFX_SET_OWORD_BIT64(_oword, _bit)				\