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find: Add find_first_andnot_bit()

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The function helps to implement cpumask_andnot() APIs.

Signed-off-by: Yury Norov [NVIDIA] <yury.norov@gmail.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: James Morse <james.morse@arm.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>
Tested-by: James Morse <james.morse@arm.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Tested-by: Fenghua Yu <fenghuay@nvidia.com>
Link: https://lore.kernel.org/20250515165855.31452-3-james.morse@arm.com
This commit is contained in:
Yury Norov [NVIDIA] 2025-05-15 16:58:32 +00:00 committed by Borislav Petkov (AMD)
parent 189572bf4e
commit 13f0a02bf4
2 changed files with 36 additions and 0 deletions
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25
include/linux/find.h
View File

@ -29,6 +29,8 @@ unsigned long __find_nth_and_andnot_bit(const unsigned long *addr1, const unsign
unsigned long n);
extern unsigned long _find_first_and_bit(const unsigned long *addr1,
const unsigned long *addr2, unsigned long size);
unsigned long _find_first_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
unsigned long size);
unsigned long _find_first_and_and_bit(const unsigned long *addr1, const unsigned long *addr2,
const unsigned long *addr3, unsigned long size);
extern unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size);
@ -347,6 +349,29 @@ unsigned long find_first_and_bit(const unsigned long *addr1,
}
#endif
/**
* find_first_andnot_bit - find the first bit set in 1st memory region and unset in 2nd
* @addr1: The first address to base the search on
* @addr2: The second address to base the search on
* @size: The bitmap size in bits
*
* Returns the bit number for the first set bit
* If no bits are set, returns >= @size.
*/
static __always_inline
unsigned long find_first_andnot_bit(const unsigned long *addr1,
const unsigned long *addr2,
unsigned long size)
{
if (small_const_nbits(size)) {
unsigned long val = *addr1 & (~*addr2) & GENMASK(size - 1, 0);
return val ? __ffs(val) : size;
}
return _find_first_andnot_bit(addr1, addr2, size);
}
/**
* find_first_and_and_bit - find the first set bit in 3 memory regions
* @addr1: The first address to base the search on

11
lib/find_bit.c
View File

@ -116,6 +116,17 @@ unsigned long _find_first_and_bit(const unsigned long *addr1,
EXPORT_SYMBOL(_find_first_and_bit);
#endif
/*
* Find the first bit set in 1st memory region and unset in 2nd.
*/
unsigned long _find_first_andnot_bit(const unsigned long *addr1,
const unsigned long *addr2,
unsigned long size)
{
return FIND_FIRST_BIT(addr1[idx] & ~addr2[idx], /* nop */, size);
}
EXPORT_SYMBOL(_find_first_andnot_bit);
/*
* Find the first set bit in three memory regions.
*/