[PATCH v2 1/6] lib: add ISO 3309 model crc64

[Kamlesh Gurudasani <kamlesh@xxxxxx>]

Add the polynomial to the crc64 table generation, and provide a
generic library routine implementing the algorithm.

64-bit cyclic redundancy checks (CRC) according to the ISO 3309 standard.

The ISO 3309 64-bit CRC model parameters are as follows:
    Generator Polynomial: x^64 + x^4 + x^3 + x + 1
    Polynomial Value: 0x000000000000001B
    Initial value: 0x0000000000000000
    Reflected Input: False
    Reflected Output: False
    Xor Final: 0x0000000000000000

Signed-off-by: Kamlesh Gurudasani <kamlesh@xxxxxx>
---
 include/linux/crc64.h |  1 +
 lib/crc64.c           | 27 +++++++++++++++++++++++++++
 lib/gen_crc64table.c  |  6 ++++++
 3 files changed, 34 insertions(+)

diff --git a/include/linux/crc64.h b/include/linux/crc64.h
index e044c60d1e61..70202da51c2c 100644
--- a/include/linux/crc64.h
+++ b/include/linux/crc64.h
@@ -10,6 +10,7 @@
 #define CRC64_ROCKSOFT_STRING "crc64-rocksoft"
 
 u64 __pure crc64_be(u64 crc, const void *p, size_t len);
+u64 __pure crc64_iso_generic(u64 crc, const void *p, size_t len);
 u64 __pure crc64_rocksoft_generic(u64 crc, const void *p, size_t len);
 
 u64 crc64_rocksoft(const unsigned char *buffer, size_t len);
diff --git a/lib/crc64.c b/lib/crc64.c
index 61ae8dfb6a1c..e066c8b2a511 100644
--- a/lib/crc64.c
+++ b/lib/crc64.c
@@ -22,6 +22,11 @@
  * x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
  * x^7 + x^4 + x + 1
  *
+ * crc64iso[256] table is from the ISO specification polynomial
+ * defined as,
+ *
+ * x^64 + x^4 + x^3 + x + 1
+ *
  * crc64rocksoft[256] table is from the Rocksoft specification polynomial
  * defined as,
  *
@@ -63,6 +68,28 @@ u64 __pure crc64_be(u64 crc, const void *p, size_t len)
 }
 EXPORT_SYMBOL_GPL(crc64_be);
 
+/**
+ * crc64_iso_generic - Calculate bitwise ISO CRC64
+ * @crc: seed value for computation. 0 for a new CRC calculation, or the
+ *	 previous crc64 value if computing incrementally.
+ * @p: pointer to buffer over which CRC64 is run
+ * @len: length of buffer @p
+ */
+u64 __pure crc64_iso_generic(u64 crc, const void *p, size_t len)
+{
+	size_t i, t;
+
+	const unsigned char *_p = p;
+
+	for (i = 0; i < len; i++) {
+		t = ((crc >> 56) ^ (*_p++)) & 0xFF;
+		crc = crc64isotable[t] ^ (crc << 8);
+	}
+
+	return crc;
+}
+EXPORT_SYMBOL_GPL(crc64_iso_generic);
+
 /**
  * crc64_rocksoft_generic - Calculate bitwise Rocksoft CRC64
  * @crc: seed value for computation. 0 for a new CRC calculation, or the
diff --git a/lib/gen_crc64table.c b/lib/gen_crc64table.c
index 55e222acd0b8..ec2add75ec8b 100644
--- a/lib/gen_crc64table.c
+++ b/lib/gen_crc64table.c
@@ -17,9 +17,11 @@
 #include <stdio.h>
 
 #define CRC64_ECMA182_POLY 0x42F0E1EBA9EA3693ULL
+#define CRC64_ISO_POLY 0x000000000000001BULL
 #define CRC64_ROCKSOFT_POLY 0x9A6C9329AC4BC9B5ULL
 
 static uint64_t crc64_table[256] = {0};
+static uint64_t crc64_iso_table[256] = {0};
 static uint64_t crc64_rocksoft_table[256] = {0};
 
 static void generate_reflected_crc64_table(uint64_t table[256], uint64_t poly)
@@ -82,6 +84,9 @@ static void print_crc64_tables(void)
 	printf("static const u64 ____cacheline_aligned crc64table[256] = {\n");
 	output_table(crc64_table);
 
+	printf("\nstatic const u64 ____cacheline_aligned crc64isotable[256] = {\n");
+	output_table(crc64_iso_table);
+
 	printf("\nstatic const u64 ____cacheline_aligned crc64rocksofttable[256] = {\n");
 	output_table(crc64_rocksoft_table);
 }
@@ -89,6 +94,7 @@ static void print_crc64_tables(void)
 int main(int argc, char *argv[])
 {
 	generate_crc64_table(crc64_table, CRC64_ECMA182_POLY);
+	generate_crc64_table(crc64_iso_table, CRC64_ISO_POLY);
 	generate_reflected_crc64_table(crc64_rocksoft_table, CRC64_ROCKSOFT_POLY);
 	print_crc64_tables();
 	return 0;

-- 
2.34.1