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bitfield.h: add FIELD_FIT() helper

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Add a helper for checking at runtime that a value will fit inside
a specified field/mask.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jakub Kicinski 2017-02-09 09:17:27 -08:00 committed by David S. Miller
parent 4f2bd6b35b
commit 1697599ee3
2 changed files with 13 additions and 2 deletions
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2
drivers/net/ethernet/netronome/nfp/nfp_bpf.h
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@ -39,8 +39,6 @@
#include <linux/list.h> #include <linux/list.h>
#include <linux/types.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 /* For branch fixup logic use up-most byte of branch instruction as scratch
* area. Remember to clear this before sending instructions to HW! * area. Remember to clear this before sending instructions to HW!
*/ */

13
include/linux/bitfield.h
View File

@ -62,6 +62,19 @@
(1ULL << __bf_shf(_mask))); \ (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 * FIELD_PREP() - prepare a bitfield element
* @_mask: shifted mask defining the field's length and position * @_mask: shifted mask defining the field's length and position