From mboxrd@z Thu Jan  1 00:00:00 1970
From: gang.chen@asianux.com (Chen Gang)
Date: Thu, 26 Sep 2013 10:00:30 +0800
Subject: [PATCH v2] ARM: include: asm: use 'long long' instead of 'u64'
 within atomic.h
In-Reply-To: <20130925160746.GC14502@mudshark.cambridge.arm.com>
References: <523D7DC7.8030603@asianux.com>
 <20130924093041.GB15119@mudshark.cambridge.arm.com>
 <5242498F.8060407@asianux.com>
 <20130925160746.GC14502@mudshark.cambridge.arm.com>
Message-ID: <5243953E.6010405@asianux.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 09/26/2013 12:07 AM, Will Deacon wrote:
> On Wed, Sep 25, 2013 at 03:25:19AM +0100, Chen Gang wrote:
>> atomic* value is signed value, and atomic* functions need also process
>> signed value (parameter value, and return value), so 32-bit arm need
>> use 'long long' instead of 'u64'.
>>
>> After replacement, it will also fix a bug for atomic64_add_negative():
>> "u64 is never less than 0".
>>
>> The modifications are:
>>
>>   in vim, use "1,% s/\<u64\>/long long/g" command.
>>   remove '__aligned(8)' which is useless for 64-bit.
>>   be sure of 80 column limitation after replacement.
>>
>>
>> Signed-off-by: Chen Gang <gang.chen@asianux.com>
> 
> Looks better to me, thanks. While you're here, we could also replace the use
> of `unsigned long' with `int' for the 32-bit atomics, then the whole header
> is consistent with the generic types.
> 
> Will
> 
> 

Hmm... at least, it seems we can let "use 'int' for 32-bit atomics" in
another patch.


Firstly, this 'fix' is not belong to API, and either, it has no related
'standard' 'demo' in "asm-generic/" (it is architecture independent, so
no related inline assembly code).

After a random check, another 3 architectures (maybe more) are also may
using 'unsigned long': "arm64/include/asm/atomic.h",
"sh/include/asm/atomic-llsc.h", and "xtensa/include/asm/atomic.h".

And as far as I know, for a register related variable, 'unsigned long'
is also a common using way for both 32-bit and 64-bit (at least, it is a
simple way to prevent issues).


Thanks.
-- 
Chen Gang