linux-kernel - Re: [PATCH] Crypto: gf128mul : fixed a parentheses coding style issue

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Date:	Mon, 13 Oct 2014 21:52:56 +0100
From:	Michael Roocroft <mike.linux@...nternet.com>
To:	Joe Perches <joe@...ches.com>
CC:	herbert@...dor.apana.org.au, davem@...emloft.net,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Crypto: gf128mul : fixed a parentheses coding style issue

On 10/13/14 21:15, Joe Perches wrote:
> On Mon, 2014-10-13 at 21:12 +0100, Michael Roocroft wrote:
>> On 10/13/14 00:01, Joe Perches wrote:
>>> On Sun, 2014-10-12 at 21:49 +0100, Mike Roocroft wrote:
>>>> Fixed a coding style issue.
>>> []
>>>> diff --git a/crypto/gf128mul.c b/crypto/gf128mul.c
>>> []
>>>> @@ -97,7 +97,7 @@
>>>>        the table above
>>>>    */
>>>>    
>>>> -#define xx(p, q)	0x##p##q
>>>> +#define xx(p, q)	(0x##p##q)
>>>>    
>>>>    #define xda_bbe(i) ( \
>>>>    	(i & 0x80 ? xx(43, 80) : 0) ^ (i & 0x40 ? xx(21, c0) : 0) ^ \
>>> I think that macro is pretty useless and nothing
>>> but obfuscation now.
>>>
>>> The comment above it doesn't seem useful either.
>>>
>>> How about just removing and replacing the uses
>>> like this?
>>>
>>> ---
>>>    crypto/gf128mul.c | 27 ++++++++-------------------
>>>    1 file changed, 8 insertions(+), 19 deletions(-)
>>>
>>> diff --git a/crypto/gf128mul.c b/crypto/gf128mul.c
>>> index 5276607..90cf17d 100644
>>> --- a/crypto/gf128mul.c
>>> +++ b/crypto/gf128mul.c
>>> @@ -88,29 +88,18 @@
>>>    	q(0xf8), q(0xf9), q(0xfa), q(0xfb), q(0xfc), q(0xfd), q(0xfe), q(0xff) \
>>>    }
>>>    
>>> -/*	Given the value i in 0..255 as the byte overflow when a field element
>>> -    in GHASH is multiplied by x^8, this function will return the values that
>>> -    are generated in the lo 16-bit word of the field value by applying the
>>> -    modular polynomial. The values lo_byte and hi_byte are returned via the
>>> -    macro xp_fun(lo_byte, hi_byte) so that the values can be assembled into
>>> -    memory as required by a suitable definition of this macro operating on
>>> -    the table above
>>> -*/
>>> -
>>> -#define xx(p, q)	0x##p##q
>>> -
>>>    #define xda_bbe(i) ( \
>>> -	(i & 0x80 ? xx(43, 80) : 0) ^ (i & 0x40 ? xx(21, c0) : 0) ^ \
>>> -	(i & 0x20 ? xx(10, e0) : 0) ^ (i & 0x10 ? xx(08, 70) : 0) ^ \
>>> -	(i & 0x08 ? xx(04, 38) : 0) ^ (i & 0x04 ? xx(02, 1c) : 0) ^ \
>>> -	(i & 0x02 ? xx(01, 0e) : 0) ^ (i & 0x01 ? xx(00, 87) : 0) \
>>> +	(i & 0x80 ? 0x4380 : 0) ^ (i & 0x40 ? 0x21c0 : 0) ^ \
>>> +	(i & 0x20 ? 0x10e0 : 0) ^ (i & 0x10 ? 0x0870 : 0) ^ \
>>> +	(i & 0x08 ? 0x0438 : 0) ^ (i & 0x04 ? 0x021c : 0) ^ \
>>> +	(i & 0x02 ? 0x010e : 0) ^ (i & 0x01 ? 0x0087 : 0) \
>>>    )
>>>    
>>>    #define xda_lle(i) ( \
>>> -	(i & 0x80 ? xx(e1, 00) : 0) ^ (i & 0x40 ? xx(70, 80) : 0) ^ \
>>> -	(i & 0x20 ? xx(38, 40) : 0) ^ (i & 0x10 ? xx(1c, 20) : 0) ^ \
>>> -	(i & 0x08 ? xx(0e, 10) : 0) ^ (i & 0x04 ? xx(07, 08) : 0) ^ \
>>> -	(i & 0x02 ? xx(03, 84) : 0) ^ (i & 0x01 ? xx(01, c2) : 0) \
>>> +	(i & 0x80 ? 0xe100 : 0) ^ (i & 0x40 ? 0x7080 : 0) ^ \
>>> +	(i & 0x20 ? 0x3840 : 0) ^ (i & 0x10 ? 0x1c20 : 0) ^ \
>>> +	(i & 0x08 ? 0x0e10 : 0) ^ (i & 0x04 ? 0x0708 : 0) ^ \
>>> +	(i & 0x02 ? 0x0384 : 0) ^ (i & 0x01 ? 0x01c2 : 0) \
>>>    )
>>>    
>>>    static const u16 gf128mul_table_lle[256] = gf128mul_dat(xda_lle);
>>>
>>>
>>>
>> Hi there,
> Hi Mike.
>
>> I'm not really contributing anything other than getting code checkpatch clean, whilst
>> I relearn C and get a feel for various parts of the kernel.
> checkpatch cleanliness, while OK for some parts of the
> kernel, should not be an end-goal.
>
> checkpatch is really a tool to "check patches".
>
> If you want to submit neatening only patches, please
> do your changes in drivers/staging/
>
> Otherwise, please look for code that isn't simply a
> style neatening bit, but something that actively makes
> reading the code easier, makes the object code smaller
> or faster, reduces complexity, adds extensibility,
> etc, etc...
>
> cheers, Joe
>
>
Hi Joe

Thanks for the Advice, I fully intend to making more meaningful contributions
when my confidence in writing C is better than it is at the moment. I'll concentrate
on making any changes to staging whilst I learn and get to grips with git, and
continue to look through the rest of the kernel tree as a learning exercise.

I am extremely new to all this and a little overwhelmed, but by looking and not doing
anyhing i'll never learn anything.

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