linux-kernel - Re: [PATCH] kfifo: remove unnecessary type check

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Date:	Fri, 26 Oct 2012 14:11:45 +0800
From:	Yuanhan Liu <yuanhan.liu@...ux.intel.com>
To:	Stefani Seibold <stefani@...bold.net>
Cc:	Yuanhan Liu <yliu.null@...il.com>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Wei Yang <weiyang@...ux.vnet.ibm.com>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH] kfifo: remove unnecessary type check

On Fri, Oct 26, 2012 at 07:38:31AM +0200, Stefani Seibold wrote:
> Am Freitag, den 26.10.2012, 09:46 +0800 schrieb Yuanhan Liu:
> > From: Yuanhan Liu <yuanhan.liu@...ux.intel.com>
> > 
> > Firstly, this kind of type check doesn't work. It does something similay
> > like following:
> > 	void * __dummy = NULL;
> > 	__buf = __dummy;
> > 
> > __dummy is defined as void *. Thus it will not trigger warnings as
> > expected.
> > 
> > Second, we don't need that kind of check. Since the prototype
> > of __kfifo_out is:
> > 	unsigned int __kfifo_out(struct __kfifo *fifo,  void *buf, unsigned int len)
> > 
> > buf is defined as void *, so we don't need do the type check. Remove it.
> > 
> > LINK: https://lkml.org/lkml/2012/10/25/386
> > LINK: https://lkml.org/lkml/2012/10/25/584
> > 
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Wei Yang <weiyang@...ux.vnet.ibm.com>
> > Cc: Stefani Seibold <stefani@...bold.net>
> > Cc: Fengguang Wu <fengguang.wu@...el.com>
> > Cc: Stephen Rothwell <sfr@...b.auug.org.au>
> > Signed-off-by: Yuanhan Liu <yuanhan.liu@...ux.intel.com>
> > ---
> >  include/linux/kfifo.h | 20 --------------------
> >  1 file changed, 20 deletions(-)
> > 
> > diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
> > index 10308c6..b8c1d03 100644
> > --- a/include/linux/kfifo.h
> > +++ b/include/linux/kfifo.h
> > @@ -390,10 +390,6 @@ __kfifo_int_must_check_helper( \
> >  	unsigned int __ret; \
> >  	const size_t __recsize = sizeof(*__tmp->rectype); \
> >  	struct __kfifo *__kfifo = &__tmp->kfifo; \
> > -	if (0) { \
> > -		typeof(__tmp->ptr_const) __dummy __attribute__ ((unused)); \
> > -		__dummy = (typeof(__val))NULL; \
> > -	} \
> >  	if (__recsize) \
> >  		__ret = __kfifo_in_r(__kfifo, __val, sizeof(*__val), \
> >  			__recsize); \
> > @@ -432,8 +428,6 @@ __kfifo_uint_must_check_helper( \
> >  	unsigned int __ret; \
> >  	const size_t __recsize = sizeof(*__tmp->rectype); \
> >  	struct __kfifo *__kfifo = &__tmp->kfifo; \
> > -	if (0) \
> > -		__val = (typeof(__tmp->ptr))0; \
> >  	if (__recsize) \
> >  		__ret = __kfifo_out_r(__kfifo, __val, sizeof(*__val), \
> >  			__recsize); \
> > @@ -473,8 +467,6 @@ __kfifo_uint_must_check_helper( \
> >  	unsigned int __ret; \
> >  	const size_t __recsize = sizeof(*__tmp->rectype); \
> >  	struct __kfifo *__kfifo = &__tmp->kfifo; \
> > -	if (0) \
> > -		__val = (typeof(__tmp->ptr))NULL; \
> >  	if (__recsize) \
> >  		__ret = __kfifo_out_peek_r(__kfifo, __val, sizeof(*__val), \
> >  			__recsize); \
> > @@ -512,10 +504,6 @@ __kfifo_uint_must_check_helper( \
> >  	unsigned long __n = (n); \
> >  	const size_t __recsize = sizeof(*__tmp->rectype); \
> >  	struct __kfifo *__kfifo = &__tmp->kfifo; \
> > -	if (0) { \
> > -		typeof(__tmp->ptr_const) __dummy __attribute__ ((unused)); \
> > -		__dummy = (typeof(__buf))NULL; \
> > -	} \
> >  	(__recsize) ?\
> >  	__kfifo_in_r(__kfifo, __buf, __n, __recsize) : \
> >  	__kfifo_in(__kfifo, __buf, __n); \
> > @@ -565,10 +553,6 @@ __kfifo_uint_must_check_helper( \
> >  	unsigned long __n = (n); \
> >  	const size_t __recsize = sizeof(*__tmp->rectype); \
> >  	struct __kfifo *__kfifo = &__tmp->kfifo; \
> > -	if (0) { \
> > -		typeof(__tmp->ptr) __dummy = NULL; \
> > -		__buf = __dummy; \
> > -	} \
> >  	(__recsize) ?\
> >  	__kfifo_out_r(__kfifo, __buf, __n, __recsize) : \
> >  	__kfifo_out(__kfifo, __buf, __n); \
> > @@ -777,10 +761,6 @@ __kfifo_uint_must_check_helper( \
> >  	unsigned long __n = (n); \
> >  	const size_t __recsize = sizeof(*__tmp->rectype); \
> >  	struct __kfifo *__kfifo = &__tmp->kfifo; \
> > -	if (0) { \
> > -		typeof(__tmp->ptr) __dummy __attribute__ ((unused)) = NULL; \
> > -		__buf = __dummy; \
> > -	} \
> >  	(__recsize) ? \
> >  	__kfifo_out_peek_r(__kfifo, __buf, __n, __recsize) : \
> >  	__kfifo_out_peek(__kfifo, __buf, __n); \
> 
> Did you tried to compile the whole kernel including all the drivers with
> your patch?

Hi Stefani,

I did a build test, it did't introduce any new compile errors and
warnings. While, I haven't tried make allmodconfig then. Does this patch
seems wrong to you?

Thanks,
Yuanhan Liu
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