From bf31ddc14f8c6bcd4987c31fe2bc9e93e433b41a Mon Sep 17 00:00:00 2001 From: Yury Norov Date: Mon, 22 Dec 2025 14:11:37 -0500 Subject: bitmap: add bitmap_weight_from() The function calculates a Hamming weight of a bitmap starting from an arbitrary bit. Signed-off-by: Yury Norov --- include/linux/bitmap.h | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) (limited to 'include/linux/bitmap.h') diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index b0395e4ccf90..9c0d1de44350 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -57,6 +57,7 @@ struct device; * bitmap_weight(src, nbits) Hamming Weight: number set bits * bitmap_weight_and(src1, src2, nbits) Hamming Weight of and'ed bitmap * bitmap_weight_andnot(src1, src2, nbits) Hamming Weight of andnot'ed bitmap + * bitmap_weight_from(src, start, end) Hamming Weight starting from @start * bitmap_set(dst, pos, nbits) Set specified bit area * bitmap_clear(dst, pos, nbits) Clear specified bit area * bitmap_find_next_zero_area(buf, len, pos, n, mask) Find bit free area @@ -479,6 +480,38 @@ unsigned long bitmap_weight_andnot(const unsigned long *src1, return __bitmap_weight_andnot(src1, src2, nbits); } +/** + * bitmap_weight_from - Hamming weight for a memory region + * @bitmap: The base address + * @start: The bitnumber to starts weighting + * @end: the bitmap size in bits + * + * Returns the number of set bits in the region. If @start >= @end, + * return >= end. + */ +static __always_inline +unsigned long bitmap_weight_from(const unsigned long *bitmap, + unsigned int start, unsigned int end) +{ + unsigned long w; + + if (unlikely(start >= end)) + return end; + + if (small_const_nbits(end)) + return hweight_long(*bitmap & GENMASK(end - 1, start)); + + bitmap += start / BITS_PER_LONG; + /* Opencode round_down() to not include math.h */ + end -= start & ~(BITS_PER_LONG - 1); + start %= BITS_PER_LONG; + w = bitmap_weight(bitmap, end); + if (start) + w -= hweight_long(*bitmap & BITMAP_LAST_WORD_MASK(start)); + + return w; +} + static __always_inline void bitmap_set(unsigned long *map, unsigned int start, unsigned int nbits) { -- cgit v1.2.3 From d57e74f10461b80c77d1678f646720f616fb8553 Mon Sep 17 00:00:00 2001 From: Yury Norov Date: Sun, 1 Mar 2026 20:11:55 -0500 Subject: bitmap: introduce bitmap_weighted_xor() The function helps to XOR bitmaps and calculate Hamming weight of the result in one pass. Reviewed-by: Aleksandr Loktionov Reviewed-by: Jacob Keller Signed-off-by: Yury Norov --- include/linux/bitmap.h | 15 +++++++++++++++ lib/bitmap.c | 7 +++++++ 2 files changed, 22 insertions(+) (limited to 'include/linux/bitmap.h') diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index 9c0d1de44350..b007d54a9036 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -46,6 +46,7 @@ struct device; * bitmap_and(dst, src1, src2, nbits) *dst = *src1 & *src2 * bitmap_or(dst, src1, src2, nbits) *dst = *src1 | *src2 * bitmap_weighted_or(dst, src1, src2, nbits) *dst = *src1 | *src2. Returns Hamming Weight of dst + * bitmap_weighted_xor(dst, src1, src2, nbits) *dst = *src1 ^ *src2. Returns Hamming Weight of dst * bitmap_xor(dst, src1, src2, nbits) *dst = *src1 ^ *src2 * bitmap_andnot(dst, src1, src2, nbits) *dst = *src1 & ~(*src2) * bitmap_complement(dst, src, nbits) *dst = ~(*src) @@ -169,6 +170,8 @@ void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1, const unsigned long *bitmap2, unsigned int nbits); unsigned int __bitmap_weighted_or(unsigned long *dst, const unsigned long *bitmap1, const unsigned long *bitmap2, unsigned int nbits); +unsigned int __bitmap_weighted_xor(unsigned long *dst, const unsigned long *bitmap1, + const unsigned long *bitmap2, unsigned int nbits); void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1, const unsigned long *bitmap2, unsigned int nbits); bool __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1, @@ -353,6 +356,18 @@ unsigned int bitmap_weighted_or(unsigned long *dst, const unsigned long *src1, } } +static __always_inline +unsigned int bitmap_weighted_xor(unsigned long *dst, const unsigned long *src1, + const unsigned long *src2, unsigned int nbits) +{ + if (small_const_nbits(nbits)) { + *dst = *src1 ^ *src2; + return hweight_long(*dst & BITMAP_LAST_WORD_MASK(nbits)); + } else { + return __bitmap_weighted_xor(dst, src1, src2, nbits); + } +} + static __always_inline void bitmap_xor(unsigned long *dst, const unsigned long *src1, const unsigned long *src2, unsigned int nbits) diff --git a/lib/bitmap.c b/lib/bitmap.c index 1b897f94e0ff..b9bfa157e095 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -363,6 +363,13 @@ unsigned int __bitmap_weighted_or(unsigned long *dst, const unsigned long *bitma } EXPORT_SYMBOL(__bitmap_weighted_or); +unsigned int __bitmap_weighted_xor(unsigned long *dst, const unsigned long *bitmap1, + const unsigned long *bitmap2, unsigned int bits) +{ + return BITMAP_WEIGHT(({dst[idx] = bitmap1[idx] ^ bitmap2[idx]; dst[idx]; }), bits); +} +EXPORT_SYMBOL(__bitmap_weighted_xor); + void __bitmap_set(unsigned long *map, unsigned int start, int len) { unsigned long *p = map + BIT_WORD(start); -- cgit v1.2.3