linux/arch/x86/include/asm/word-at-a-time.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_WORD_AT_A_TIME_H
#define _ASM_WORD_AT_A_TIME_H

#include <linux/bitops.h>
#include <linux/wordpart.h>

struct word_at_a_time { … };

#define WORD_AT_A_TIME_CONSTANTS …

/* Return nonzero if it has a zero */
static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c)
{ … }

static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c)
{ … }

#ifdef CONFIG_64BIT

/* Keep the initial has_zero() value for both bitmask and size calc */
#define create_zero_mask(bits) …

static inline unsigned long zero_bytemask(unsigned long bits)
{ … }

#define find_zero(bits) …

#else

/* Create the final mask for both bytemask and size */
static inline unsigned long create_zero_mask(unsigned long bits)
{
	bits = (bits - 1) & ~bits;
	return bits >> 7;
}

/* The mask we created is directly usable as a bytemask */
#define zero_bytemask …

/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
static inline unsigned long find_zero(unsigned long mask)
{
	/* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
	long a = (0x0ff0001+mask) >> 23;
	/* Fix the 1 for 00 case */
	return a & mask;
}

#endif

/*
 * Load an unaligned word from kernel space.
 *
 * In the (very unlikely) case of the word being a page-crosser
 * and the next page not being mapped, take the exception and
 * return zeroes in the non-existing part.
 */
static inline unsigned long load_unaligned_zeropad(const void *addr)
{ … }

#endif /* _ASM_WORD_AT_A_TIME_H */