From mboxrd@z Thu Jan  1 00:00:00 1970
From: gang.chen@asianux.com (Chen Gang)
Date: Tue, 01 Oct 2013 10:05:27 +0800
Subject: [PATCH 2/2] ARM: include: asm: use 'int' instead of 'unsigned
 long' for normal register variables within atomic.h
In-Reply-To: <20130930161149.GI26036@mudshark.cambridge.arm.com>
References: <20130924093041.GB15119@mudshark.cambridge.arm.com>
 <5242498F.8060407@asianux.com>
 <20130925160746.GC14502@mudshark.cambridge.arm.com>
 <5243953E.6010405@asianux.com>
 <20130926100422.GE2855@mudshark.cambridge.arm.com>
 <5244148F.6080405@asianux.com>
 <20130927110618.GB9520@mudshark.cambridge.arm.com>
 <5247A1D1.6080505@asianux.com> <5247A1FA.4030305@asianux.com>
 <5247A3FC.9020508@asianux.com>
 <20130930161149.GI26036@mudshark.cambridge.arm.com>
Message-ID: <524A2DE7.8040208@asianux.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 10/01/2013 12:11 AM, Will Deacon wrote:
> On Sun, Sep 29, 2013 at 04:52:28AM +0100, Chen Gang wrote:
>> "arc/arm" will be never on 64-bit, it is mainly on 32-bit (may also can
>> be on 16-bit).
>>
>> So better to use 'int' instead of 'unsigned long' for normal register
>> variable (on 16-bit, 'int' is allowed to be 16-bit, so historically,
>> often use 'int' for normal register variables).
> 
> This commit message doesn't make a blind bit of sense! arch/arm/ is a 32-bit
> architecture in the sense that int will always be 32-bit there. This patch
> is just a cosmetic change, bringing our atomic_t manipulation code inline
> with the atomic_t type definition.
> 

OK, thanks. That means: "arm means arm 32-bit, arm64 means arm 64-bit.
The current Linux kernel main line does not support arm 16-bit".

Since "bringing our atomic_t ... with the atomic_t type definition", can
we use 'atomic_t" instead of 'unsigned long'?

And can we use 'atomic64_t" instead of 'unsigned long' in atomic64_*()?


>> @@ -297,7 +297,7 @@ static inline void atomic64_set(atomic64_t *v, long
>> long i)
>>  static inline void atomic64_add(long long i, atomic64_t *v)
>>  {
>>  	long long result;
>> -	unsigned long tmp;
>> +	int tmp;
> 
> Please leave the atomic64_* functions alone here; the reasoning I explained
> above doesn't apply to them. Whilst int may work, it seems gratuitous to
> make this change for no reason.
> 

For 32-bit, it seems we can not use 'atomic64_t' instead of 'unsigned
long' in atomic64_*().  ;-)

For 32-bit, the original 'unsigned long' in atomic64_add() is correct,
or is also a bug?


> Will
> 
> 

In fact, if arm only for 32-bit, I really don't know why we need 'int'
instead of some 'unsigned long' (neither can let patch comment correct,
nor know which 'unsigned long' need be instead of).  :-(

It seems we need be careful to not let this patch make new bug for arm.



Thanks.
-- 
Chen Gang