lib/bitops.h

#ifndef _BITOPS_H_
#define _BITOPS_H_

#include <stdbool.h>
#include <stddef.h>

/*
 * Adapted from
 *   include/linux/bitops.h
 *
 * Copyright (C) 2017, Red Hat Inc, Andrew Jones <drjones@redhat.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2.
 */

#define BITS_PER_LONG_LONG	64
#define BIT(nr)			(1UL << (nr))
#define BIT_ULL(nr)		(1ULL << (nr))
#define BIT_MASK(nr)		(1UL << ((nr) % BITS_PER_LONG))
#define BIT_WORD(nr)		((nr) / BITS_PER_LONG)
#define BIT_ULL_MASK(nr)	(1ULL << ((nr) % BITS_PER_LONG_LONG))
#define BIT_ULL_WORD(nr)	((nr) / BITS_PER_LONG_LONG)
#define BITS_PER_BYTE		8
#define BITS_TO_LONGS(nr)	DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long))

#include <asm/bitops.h>

/*
 * Create a contiguous bitmask starting at bit position @l and ending at
 * position @h. For example
 * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
 */
#define GENMASK(h, l) \
	(((~0UL) << (l)) & (~0UL >> (BITS_PER_LONG - 1 - (h))))

#define GENMASK_ULL(h, l) \
	(((~0ULL) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))

#define upper_32_bits(n) ((u32)(((n) >> 16) >> 16))
#define lower_32_bits(n) ((u32)(n))

#ifndef HAVE_BUILTIN_FLS
static inline unsigned long fls(unsigned long word)
{
	int num = BITS_PER_LONG - 1;

#if BITS_PER_LONG == 64
	if (!(word & (~0ul << 32))) {
		num -= 32;
		word <<= 32;
	}
#endif
	if (!(word & (~0ul << (BITS_PER_LONG-16)))) {
		num -= 16;
		word <<= 16;
	}
	if (!(word & (~0ul << (BITS_PER_LONG-8)))) {
		num -= 8;
		word <<= 8;
	}
	if (!(word & (~0ul << (BITS_PER_LONG-4)))) {
		num -= 4;
		word <<= 4;
	}
	if (!(word & (~0ul << (BITS_PER_LONG-2)))) {
		num -= 2;
		word <<= 2;
	}
	if (!(word & (~0ul << (BITS_PER_LONG-1))))
		num -= 1;
	return num;
}
#else
static inline unsigned long fls(unsigned long word)
{
	return BITS_PER_LONG - __builtin_clzl(word) - 1;
}
#endif

static inline bool is_power_of_2(unsigned long n)
{
	return n && !(n & (n - 1));
}

static inline unsigned int get_order(size_t size)
{
	return size ? fls(size) + !is_power_of_2(size) : 0;
}

#endif