Viewing file:  cmpxchg-xchg.h (1.24 KB) -rw-r--r--
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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __ASM_SH_CMPXCHG_XCHG_H
#define __ASM_SH_CMPXCHG_XCHG_H
/*
* Copyright (C) 2016 Red Hat, Inc.
* Author: Michael S. Tsirkin <mst@redhat.com>
*/
#include <linux/bits.h>
#include <linux/compiler.h>
#include <asm/byteorder.h>
/*
* Portable implementations of 1 and 2 byte xchg using a 4 byte cmpxchg.
* Note: this header isn't self-contained: before including it, __cmpxchg_u32
* must be defined first.
*/
static inline u32 __xchg_cmpxchg(volatile void *ptr, u32 x, int size)
{
int off = (unsigned long)ptr % sizeof(u32);
volatile u32 *p = ptr - off;
#ifdef __BIG_ENDIAN
int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
#else
int bitoff = off * BITS_PER_BYTE;
#endif
u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
u32 oldv, newv;
u32 ret;
do {
oldv = READ_ONCE(*p);
ret = (oldv & bitmask) >> bitoff;
newv = (oldv & ~bitmask) | (x << bitoff);
} while (__cmpxchg_u32(p, oldv, newv) != oldv);
return ret;
}
static inline unsigned long xchg_u16(volatile u16 *m, unsigned long val)
{
return __xchg_cmpxchg(m, val, sizeof *m);
}
static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val)
{
return __xchg_cmpxchg(m, val, sizeof *m);
}
#endif /* __ASM_SH_CMPXCHG_XCHG_H */
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