Re: [PATCH 1/5] kfifo: remove unnecessary type check

[Stefani Seibold <stefani@seibold.net>]

Am Dienstag, den 08.01.2013, 22:57 +0800 schrieb Yuanhan Liu:
> Firstly, this kind of type check doesn't work. It does something similar
> as 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.
> 

Thats wrong.

First the type checking will be used in kfifo_put() and kfifo_in() for
const types to check if the passed type of the data can converted to the
fifo element type. 
And it will be used in kfifo_get(), kfifo_peek(), kfifo_out() and
kfio_out_peek() to check if the element type of the fifo can be
converted to the passed type of the destination.

So a big NAK!  

> v2: remove ptr and const_ptr, which were used for type checking.
> 
> LINK: https://lkml.org/lkml/2012/10/25/386
> LINK: https://lkml.org/lkml/2012/10/25/584
> 
> Cc: Stefani Seibold <stefani@seibold.net>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> ---
>  include/linux/kfifo.h |   46 ++++++++++++----------------------------------
>  1 files changed, 12 insertions(+), 34 deletions(-)
> 
> diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
> index 10308c6..7a18245 100644
> --- a/include/linux/kfifo.h
> +++ b/include/linux/kfifo.h
> @@ -63,49 +63,47 @@ struct __kfifo {
>  	void		*data;
>  };
>  
> -#define __STRUCT_KFIFO_COMMON(datatype, recsize, ptrtype) \
> +#define __STRUCT_KFIFO_COMMON(datatype, recsize) \
>  	union { \
>  		struct __kfifo	kfifo; \
>  		datatype	*type; \
>  		char		(*rectype)[recsize]; \
> -		ptrtype		*ptr; \
> -		const ptrtype	*ptr_const; \
>  	}
>  
> -#define __STRUCT_KFIFO(type, size, recsize, ptrtype) \
> +#define __STRUCT_KFIFO(type, size, recsize) \
>  { \
> -	__STRUCT_KFIFO_COMMON(type, recsize, ptrtype); \
> +	__STRUCT_KFIFO_COMMON(type, recsize); \
>  	type		buf[((size < 2) || (size & (size - 1))) ? -1 : size]; \
>  }
>  
>  #define STRUCT_KFIFO(type, size) \
> -	struct __STRUCT_KFIFO(type, size, 0, type)
> +	struct __STRUCT_KFIFO(type, size, 0)
>  
> -#define __STRUCT_KFIFO_PTR(type, recsize, ptrtype) \
> +#define __STRUCT_KFIFO_PTR(type, recsize) \
>  { \
> -	__STRUCT_KFIFO_COMMON(type, recsize, ptrtype); \
> +	__STRUCT_KFIFO_COMMON(type, recsize); \
>  	type		buf[0]; \
>  }
>  
>  #define STRUCT_KFIFO_PTR(type) \
> -	struct __STRUCT_KFIFO_PTR(type, 0, type)
> +	struct __STRUCT_KFIFO_PTR(type, 0)
>  
>  /*
>   * define compatibility "struct kfifo" for dynamic allocated fifos
>   */
> -struct kfifo __STRUCT_KFIFO_PTR(unsigned char, 0, void);
> +struct kfifo __STRUCT_KFIFO_PTR(unsigned char, 0);
>  
>  #define STRUCT_KFIFO_REC_1(size) \
> -	struct __STRUCT_KFIFO(unsigned char, size, 1, void)
> +	struct __STRUCT_KFIFO(unsigned char, size, 1)
>  
>  #define STRUCT_KFIFO_REC_2(size) \
> -	struct __STRUCT_KFIFO(unsigned char, size, 2, void)
> +	struct __STRUCT_KFIFO(unsigned char, size, 2)
>  
>  /*
>   * define kfifo_rec types
>   */
> -struct kfifo_rec_ptr_1 __STRUCT_KFIFO_PTR(unsigned char, 1, void);
> -struct kfifo_rec_ptr_2 __STRUCT_KFIFO_PTR(unsigned char, 2, void);
> +struct kfifo_rec_ptr_1 __STRUCT_KFIFO_PTR(unsigned char, 1);
> +struct kfifo_rec_ptr_2 __STRUCT_KFIFO_PTR(unsigned char, 2);
>  
>  /*
>   * helper macro to distinguish between real in place fifo where the fifo
> @@ -390,10 +388,6 @@ __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 +426,6 @@ __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 +465,6 @@ __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 +502,6 @@ __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 +551,6 @@ __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 +759,6 @@ __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); \