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

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Message-ID: <ZroZelxS_ddHwH30@kekkonen.localdomain>
Date: Mon, 12 Aug 2024 14:17:30 +0000
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Zijun Hu <zijun_hu@...oud.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jason Gunthorpe <jgg@...pe.ca>,
	"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()

Hi Andy, Zijun,

On Fri, Aug 09, 2024 at 02:27:23PM +0300, 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.

In the const case it's actually required whereas container_of() already
does exactly the same cast, rendering the cast done below redundant.
There's nothing inconsistent in removing a needless cast.

Removing it is my preference as well.

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

-- 
Kind regards,

Sakari Ailus