bitops.h

来自「U-boot源码 ARM7启动代码」· C头文件 代码 · 共 58 行

/*
 * bitops.h: Bit string operations on the m68k
 */

#ifndef _M68K_BITOPS_H
#define _M68K_BITOPS_H

#include <linux/config.h>
#include <asm/byteorder.h>

extern void set_bit(int nr, volatile void *addr);
extern void clear_bit(int nr, volatile void *addr);
extern void change_bit(int nr, volatile void *addr);
extern int test_and_set_bit(int nr, volatile void *addr);
extern int test_and_clear_bit(int nr, volatile void *addr);
extern int test_and_change_bit(int nr, volatile void *addr);

#ifdef __KERNEL__

/*
 * ffs: find first bit set. This is defined the same way as
 * the libc and compiler builtin ffs routines, therefore
 * differs in spirit from the above ffz (man ffs).
 */
extern __inline__ int ffs(int x)
{
	int r = 1;

	if (!x)
		return 0;
	if (!(x & 0xffff)) {
		x >>= 16;
		r += 16;
	}
	if (!(x & 0xff)) {
		x >>= 8;
		r += 8;
	}
	if (!(x & 0xf)) {
		x >>= 4;
		r += 4;
	}
	if (!(x & 3)) {
		x >>= 2;
		r += 2;
	}
	if (!(x & 1)) {
		x >>= 1;
		r += 1;
	}
	return r;
}
#define __ffs(x) (ffs(x) - 1)

#endif /* __KERNEL__ */

#endif /* _M68K_BITOPS_H */