docs: driver-api: usb: avoid using ReST :doc:`foo` markup
[linux-2.6-microblaze.git] / lib / gen_crc64table.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Generate lookup table for the table-driven CRC64 calculation.
4  *
5  * gen_crc64table is executed in kernel build time and generates
6  * lib/crc64table.h. This header is included by lib/crc64.c for
7  * the table-driven CRC64 calculation.
8  *
9  * See lib/crc64.c for more information about which specification
10  * and polynomial arithmetic that gen_crc64table.c follows to
11  * generate the lookup table.
12  *
13  * Copyright 2018 SUSE Linux.
14  *   Author: Coly Li <colyli@suse.de>
15  */
16 #include <inttypes.h>
17 #include <stdio.h>
18
19 #define CRC64_ECMA182_POLY 0x42F0E1EBA9EA3693ULL
20
21 static uint64_t crc64_table[256] = {0};
22
23 static void generate_crc64_table(void)
24 {
25         uint64_t i, j, c, crc;
26
27         for (i = 0; i < 256; i++) {
28                 crc = 0;
29                 c = i << 56;
30
31                 for (j = 0; j < 8; j++) {
32                         if ((crc ^ c) & 0x8000000000000000ULL)
33                                 crc = (crc << 1) ^ CRC64_ECMA182_POLY;
34                         else
35                                 crc <<= 1;
36                         c <<= 1;
37                 }
38
39                 crc64_table[i] = crc;
40         }
41 }
42
43 static void print_crc64_table(void)
44 {
45         int i;
46
47         printf("/* this file is generated - do not edit */\n\n");
48         printf("#include <linux/types.h>\n");
49         printf("#include <linux/cache.h>\n\n");
50         printf("static const u64 ____cacheline_aligned crc64table[256] = {\n");
51         for (i = 0; i < 256; i++) {
52                 printf("\t0x%016" PRIx64 "ULL", crc64_table[i]);
53                 if (i & 0x1)
54                         printf(",\n");
55                 else
56                         printf(", ");
57         }
58         printf("};\n");
59 }
60
61 int main(int argc, char *argv[])
62 {
63         generate_crc64_table();
64         print_crc64_table();
65         return 0;
66 }