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kernel/linux-imx6_3.14.28/include/asm-generic/bitops/ffs.h 615 Bytes
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  #ifndef _ASM_GENERIC_BITOPS_FFS_H_
  #define _ASM_GENERIC_BITOPS_FFS_H_
  
  /**
   * ffs - find first bit set
   * @x: the word to search
   *
   * This is defined the same way as
   * the libc and compiler builtin ffs routines, therefore
   * differs in spirit from the above ffz (man ffs).
   */
  static 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;
  }
  
  #endif /* _ASM_GENERIC_BITOPS_FFS_H_ */