Thread (20 messages) 20 messages, 7 authors, 2018-07-24

Re: [PATCH v3 1/3] lib: add crc64 calculation routines

From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Date: 2018-07-17 15:43:12
Also in: lkml

On Tue, 2018-07-17 at 22:55 +0800, Coly Li wrote:
This patch adds the re-write crc64 calculation routines for Linux
kernel.
The CRC64 polynomical arithmetic follows ECMA-182 specification,
inspired
by CRC paper of Dr. Ross N. Williams
(see http://www.ross.net/crc/download/crc_v3.txt) and other public
domain
implementations.

All the changes work in this way,
- When Linux kernel is built, host program lib/gen_crc64table.c will
be
  compiled to lib/gen_crc64table and executed.
- The output of gen_crc64table execution is an array called as lookup
  table (a.k.a POLY 0x42f0e1eba9ea369) which contain 256 64bits-long
  numbers, this talbe is dumped into header file lib/crc64table.h.
- Then the header file is included by lib/crc64.c for normal 64bit crc
  calculation.
- Function declaration of the crc64 calculation routines is placed in
  include/linux/crc64.h
Thanks for an update! My comments below.
Co-developed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
As required by coding style this tag should be accompanied with SoB of
co-developer(s).
+u64 __pure crc64_update(u64 crc, const void *_p, size_t len);
For sake of consistency I would name _len as well.
+ * Normal 64bit CRC calculation.
I think 64-bit form is slightly better and more often

$ git grep -n -w 64bit | wc -l
809

$ git grep -n -w 64-bit | wc -l
2957
+ * crc64table[256] is the lookup table of a table-driver 64bit CRC
Ditto.
+ * Copyright 2018 SUSE Linux.
+ *   Author: Coly Li [off-list ref]
+ *
This (blank comment) line is not needed.
+u64 __pure crc64_update(u64 crc, const void *_p, size_t len)
_len ?
+ * Copyright 2018 SUSE Linux.
+ *   Author: Coly Li [off-list ref]
+ *
Not needed line.

+#include <inttypes.h>
+#include <stdio.h>
+ blank line? Would separate groups of headers logically.
+#include <linux/swab.h>
+static int64_t crc64_table[256] = {0,};
I guess {0} would work as well (no comma).
+	printf("#include <uapi/linux/types.h>\n");
+	printf("#include <linux/cache.h>\n\n");
Do wee need these? CRC32 case seems fine without.

-- 
Andy Shevchenko [off-list ref]
Intel Finland Oy
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