linux-kernel - Re: [PATCH] linux/container_of.h: Remove redundant type cast in container_of

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Message-ID: <ff11cab0-6dfd-407c-8039-3dfd873e7280@icloud.com>
Date: Fri, 9 Aug 2024 20:04:57 +0800
From: Zijun Hu <zijun_hu@...oud.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Jason Gunthorpe <jgg@...pe.ca>, Sakari Ailus <sakari.ailus@...ux.intel.com>,
 "Matthew Wilcox (Oracle)" <willy@...radead.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>, linux-kernel@...r.kernel.org,
 Zijun Hu <quic_zijuhu@...cinc.com>
Subject: Re: [PATCH] linux/container_of.h: Remove redundant type cast in
 container_of_const()

On 2024/8/9 19:27, Andy Shevchenko wrote:
> On Fri, Aug 02, 2024 at 11:15:15PM +0800, Zijun Hu wrote:
>> From: Zijun Hu <quic_zijuhu@...cinc.com>
>>
>> Remove redundant (type *) cast for default branch in container_of_const()
>> since the cast has been done by container_of().
> 
> While it might have same effect, the below is explicitly clear about both
> cases. With your patch it will become inconsistent.
> 

my change is more obvious to say that container_of_const() is same as
container_of() for none const pointer parameter @ptr. it is simpler and
easier to understand.

> ...
> 
>>  #define container_of_const(ptr, type, member)				\
>>  	_Generic(ptr,							\
>>  		const typeof(*(ptr)) *: ((const type *)container_of(ptr, type, member)),\
> 
> (see, in the above line the cast is still present / required)
> 

yes, for above case, (const type *) is suitable and required.

>> -		default: ((type *)container_of(ptr, type, member))	\
>> +		default: container_of(ptr, type, member)	\
>>  	)
>