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kernel/linux-rt-4.4.41/arch/arm/include/uapi/asm/swab.h 1.36 KB
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  /*
   *  arch/arm/include/asm/byteorder.h
   *
   * ARM Endian-ness.  In little endian mode, the data bus is connected such
   * that byte accesses appear as:
   *  0 = d0...d7, 1 = d8...d15, 2 = d16...d23, 3 = d24...d31
   * and word accesses (data or instruction) appear as:
   *  d0...d31
   *
   * When in big endian mode, byte accesses appear as:
   *  0 = d24...d31, 1 = d16...d23, 2 = d8...d15, 3 = d0...d7
   * and word accesses (data or instruction) appear as:
   *  d0...d31
   */
  #ifndef _UAPI__ASM_ARM_SWAB_H
  #define _UAPI__ASM_ARM_SWAB_H
  
  #include <linux/compiler.h>
  #include <linux/types.h>
  
  #if !defined(__STRICT_ANSI__) || defined(__KERNEL__)
  #  define __SWAB_64_THRU_32__
  #endif
  
  
  #if !defined(__KERNEL__) || __LINUX_ARM_ARCH__ < 6
  static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
  {
  	__u32 t;
  
  #ifndef __thumb__
  	if (!__builtin_constant_p(x)) {
  		/*
  		 * The compiler needs a bit of a hint here to always do the
  		 * right thing and not screw it up to different degrees
  		 * depending on the gcc version.
  		 */
  		asm ("eor\t%0, %1, %1, ror #16" : "=r" (t) : "r" (x));
  	} else
  #endif
  		t = x ^ ((x << 16) | (x >> 16)); /* eor r1,r0,r0,ror #16 */
  
  	x = (x << 24) | (x >> 8);		/* mov r0,r0,ror #8      */
  	t &= ~0x00FF0000;			/* bic r1,r1,#0x00FF0000 */
  	x ^= (t >> 8);				/* eor r0,r0,r1,lsr #8   */
  
  	return x;
  }
  #define __arch_swab32 __arch_swab32
  
  #endif
  
  #endif /* _UAPI__ASM_ARM_SWAB_H */