linux-kernel - Re: [PATCH v2 1/3] lib: add crc64 calculation routines

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Date:   Tue, 17 Jul 2018 22:19:05 +0800
From:   Coly Li <colyli@...e.de>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-kernel@...r.kernel.org
Cc:     linux-bcache@...r.kernel.org, linux-block@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michael Lyle <mlyle@...e.org>,
        Kent Overstreet <kent.overstreet@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kate Stewart <kstewart@...uxfoundation.org>
Subject: Re: [PATCH v2 1/3] lib: add crc64 calculation routines

On 2018/7/17 5:57 PM, Andy Shevchenko wrote:
> On Tue, 2018-07-17 at 14:57 +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
> 
>> + * crc64.h
>> + *
> 
> Do we need file name in the file?
> 

Not mandatory, I remove it in v3 series.

>> + * See lib/crc64.c for the related specification and polynomical
>> arithmetic.
>> + */
> 
>> +// SPDX-License-Identifier: GPL-2.0
> 
>> +#include <linux/module.h>
>> +#include <uapi/linux/types.h>
> 
> Why not simple linux/types.h ?

Yes linux/types.h works, I use this one.

> 
>> +#include "crc64table.h"
>> +
>> +MODULE_DESCRIPTION("CRC64 calculations");
> 
>> +MODULE_LICENSE("GPL");
> 
> License mismatch with SPDX.
> 

It is "GPL v2" in v3 series.

>> +#include <inttypes.h>
>> +#include <linux/swab.h>
>> +#include <stdio.h>
> 
> I would follow the common grouping of the headers, like more generic
> first, more particular last:
> 
> inttupes
> stdio
> 
> linux/foo
> 
> asm/bar
> 

Now it is in the following order,
#include <inttypes.h>
#include <stdio.h>
#include <linux/swab.h>

>> +#include "../usr/include/asm/byteorder.h"
> 
> Hmm...
In v3 series, I don't use __le64 and cpu_to_le64(), so this header is
not necessary. It does not exist in v3 series.

Thanks.

Coly Li