56  * @crc: seed value for computation.  ~0 for Ethernet, sometimes 0 for
58  * @p: pointer to buffer over which CRC is run
61 u32  crc32_le(u32 crc, unsigned char const *p, size_t len);
69 u32 crc32_le(u32 crc, unsigned char const *p, size_t len)  in crc32_le()  argument
73 		crc ^= *p++;  in crc32_le()
75 			crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);  in crc32_le()
77 	return crc;  in crc32_le()
81 u32 crc32_le(u32 crc, unsigned char const *p, size_t len)  in crc32_le()  argument
88 #  define DO_CRC(x) crc = tab[ (crc ^ (x)) & 255 ] ^ (crc>>8)  in crc32_le()
90 #  define DO_CRC(x) crc = tab[ ((crc >> 24) ^ (x)) & 255] ^ (crc<<8)  in crc32_le()
92 	/* printf("Crc32_le crc=%x\n",crc); */  in crc32_le()
93 	crc = __cpu_to_le32(crc);  in crc32_le()
108 			crc ^= *++b;  in crc32_le()
126 	return __le32_to_cpu(crc);  in crc32_le()
132 		crc ^= *p++;  in crc32_le()
133 		crc = (crc >> 4) ^ crc32table_le[crc & 15];  in crc32_le()
134 		crc = (crc >> 4) ^ crc32table_le[crc & 15];  in crc32_le()
136 	return crc;  in crc32_le()
139 		crc ^= *p++;  in crc32_le()
140 		crc = (crc >> 2) ^ crc32table_le[crc & 3];  in crc32_le()
141 		crc = (crc >> 2) ^ crc32table_le[crc & 3];  in crc32_le()
142 		crc = (crc >> 2) ^ crc32table_le[crc & 3];  in crc32_le()
143 		crc = (crc >> 2) ^ crc32table_le[crc & 3];  in crc32_le()
145 	return crc;  in crc32_le()
152  * @crc: seed value for computation.  ~0 for Ethernet, sometimes 0 for
154  * @p: pointer to buffer over which CRC is run
157 u32 __attribute_pure__ crc32_be(u32 crc, unsigned char const *p, size_t len);
165 u32 __attribute_pure__ crc32_be(u32 crc, unsigned char const *p, size_t len)  in crc32_be()  argument
169 		crc ^= *p++ << 24;  in crc32_be()
171 			crc =  in crc32_be()
172 			    (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE :  in crc32_be()
175 	return crc;  in crc32_be()
179 u32 __attribute_pure__ crc32_be(u32 crc, unsigned char const *p, size_t len)  in crc32_be()  argument
186 #  define DO_CRC(x) crc = tab[ (crc ^ (x)) & 255 ] ^ (crc>>8)  in crc32_be()
188 #  define DO_CRC(x) crc = tab[ ((crc >> 24) ^ (x)) & 255] ^ (crc<<8)  in crc32_be()
191 	crc = __cpu_to_be32(crc);  in crc32_be()
206 			crc ^= *++b;  in crc32_be()
223 	return __be32_to_cpu(crc);  in crc32_be()
229 		crc ^= *p++ << 24;  in crc32_be()
230 		crc = (crc << 4) ^ crc32table_be[crc >> 28];  in crc32_be()
231 		crc = (crc << 4) ^ crc32table_be[crc >> 28];  in crc32_be()
233 	return crc;  in crc32_be()
236 		crc ^= *p++ << 24;  in crc32_be()
237 		crc = (crc << 2) ^ crc32table_be[crc >> 30];  in crc32_be()
238 		crc = (crc << 2) ^ crc32table_be[crc >> 30];  in crc32_be()
239 		crc = (crc << 2) ^ crc32table_be[crc >> 30];  in crc32_be()
240 		crc = (crc << 2) ^ crc32table_be[crc >> 30];  in crc32_be()
242 	return crc;  in crc32_be()
251  * A brief CRC tutorial.
253  * A CRC is a long-division remainder.  You add the CRC to the message,
254  * and the whole thing (message+CRC) is a multiple of the given
255  * CRC polynomial.  To check the CRC, you can either check that the
256  * CRC matches the recomputed value, *or* you can check that the
257  * remainder computed on the message+CRC is 0.  This latter approach
259  * protocols put the end-of-frame flag after the CRC.
267  * A 32-bit CRC polynomial is actually 33 bits long.  But since it's
268  * 33 bits long, bit 32 is always going to be set, so usually the CRC
272  * Note that a CRC is computed over a string of *bits*, so you have
277  * is sent last.  And when appending a CRC word to a message, you should
281  * the divisor (the CRC polynomial) you're dividing by.  Each step of the
288  * When computing a CRC, we don't care about the quotient, so we can
293  * A big-endian CRC written this way would be coded like:
304  * Also, to add the CRC to a message, we need a 32-bit-long hole for it at
310  * and merging in the final 32 zero bits to make room for the CRC can be
362  * generator polynomial.  This is simply the CRC-32 of the given
367  * polynomial.  To enable a CRC to detect this condition, it's common to
368  * invert the CRC before appending it.  This makes the remainder of the
369  * message+crc come out not as zero, but some fixed non-zero value.
427  * This checks that CRC(buf + CRC(buf)) = 0, and that
428  * CRC commutes with bit-reversal.  This has the side effect
430  * the CRC of the reversed buffer.
500 		/* Now check that CRC(buf1 ^ buf2) = CRC(buf1) ^ CRC(buf2) */  in main()
503 			printf("CRC XOR fail: 0x%08x != 0x%08x ^ 0x%08x\n",  in main()