bitfield.h: add FIELD_FIT() helper

Add a helper for checking at runtime that a value will fit inside a specified field/mask. Signed-off-by: Jakub Kicinski <[email protected]> Signed-off-by: David S. Miller <[email protected]>
akeromi · Feb 10, 2017 · 1697599 · 1697599
1 parent 4f2bd6b
commit 1697599
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diff --git a/drivers/net/ethernet/netronome/nfp/nfp_bpf.h b/drivers/net/ethernet/netronome/nfp/nfp_bpf.h
@@ -39,8 +39,6 @@
 #include <linux/list.h>
 #include <linux/types.h>
 
-#define FIELD_FIT(mask, val)  (!((((u64)val) << __bf_shf(mask)) & ~(mask)))
-
 /* For branch fixup logic use up-most byte of branch instruction as scratch
  * area.  Remember to clear this before sending instructions to HW!
  */

diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
@@ -62,6 +62,19 @@
 					      (1ULL << __bf_shf(_mask))); \
 	})
 
+/**
+ * FIELD_FIT() - check if value fits in the field
+ * @_mask: shifted mask defining the field's length and position
+ * @_val:  value to test against the field
+ *
+ * Return: true if @_val can fit inside @_mask, false if @_val is too big.
+ */
+#define FIELD_FIT(_mask, _val)						\
+	({								\
+		__BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_FIT: ");	\
+		!((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
+	})
+
 /**
  * FIELD_PREP() - prepare a bitfield element
  * @_mask: shifted mask defining the field's length and position