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kernel/linux-imx6_3.14.28/lib/crc32defs.h 2.01 KB
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  /*
   * There are multiple 16-bit CRC polynomials in common use, but this is
   * *the* standard CRC-32 polynomial, first popularized by Ethernet.
   * x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x^1+x^0
   */
  #define CRCPOLY_LE 0xedb88320
  #define CRCPOLY_BE 0x04c11db7
  
  /*
   * This is the CRC32c polynomial, as outlined by Castagnoli.
   * x^32+x^28+x^27+x^26+x^25+x^23+x^22+x^20+x^19+x^18+x^14+x^13+x^11+x^10+x^9+
   * x^8+x^6+x^0
   */
  #define CRC32C_POLY_LE 0x82F63B78
  
  /* Try to choose an implementation variant via Kconfig */
  #ifdef CONFIG_CRC32_SLICEBY8
  # define CRC_LE_BITS 64
  # define CRC_BE_BITS 64
  #endif
  #ifdef CONFIG_CRC32_SLICEBY4
  # define CRC_LE_BITS 32
  # define CRC_BE_BITS 32
  #endif
  #ifdef CONFIG_CRC32_SARWATE
  # define CRC_LE_BITS 8
  # define CRC_BE_BITS 8
  #endif
  #ifdef CONFIG_CRC32_BIT
  # define CRC_LE_BITS 1
  # define CRC_BE_BITS 1
  #endif
  
  /*
   * How many bits at a time to use.  Valid values are 1, 2, 4, 8, 32 and 64.
   * For less performance-sensitive, use 4 or 8 to save table size.
   * For larger systems choose same as CPU architecture as default.
   * This works well on X86_64, SPARC64 systems. This may require some
   * elaboration after experiments with other architectures.
   */
  #ifndef CRC_LE_BITS
  #  ifdef CONFIG_64BIT
  #  define CRC_LE_BITS 64
  #  else
  #  define CRC_LE_BITS 32
  #  endif
  #endif
  #ifndef CRC_BE_BITS
  #  ifdef CONFIG_64BIT
  #  define CRC_BE_BITS 64
  #  else
  #  define CRC_BE_BITS 32
  #  endif
  #endif
  
  /*
   * Little-endian CRC computation.  Used with serial bit streams sent
   * lsbit-first.  Be sure to use cpu_to_le32() to append the computed CRC.
   */
  #if CRC_LE_BITS > 64 || CRC_LE_BITS < 1 || CRC_LE_BITS == 16 || \
  	CRC_LE_BITS & CRC_LE_BITS-1
  # error "CRC_LE_BITS must be one of {1, 2, 4, 8, 32, 64}"
  #endif
  
  /*
   * Big-endian CRC computation.  Used with serial bit streams sent
   * msbit-first.  Be sure to use cpu_to_be32() to append the computed CRC.
   */
  #if CRC_BE_BITS > 64 || CRC_BE_BITS < 1 || CRC_BE_BITS == 16 || \
  	CRC_BE_BITS & CRC_BE_BITS-1
  # error "CRC_BE_BITS must be one of {1, 2, 4, 8, 32, 64}"
  #endif