linux-kernel - Re: [PATCH 3/5] driver core: make struct device

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Message-ID: <Y35enjI+dhhqiG3B@ziepe.ca>
Date:   Wed, 23 Nov 2022 13:55:42 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Maximilian Luz <luzmaximilian@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Stefan Richter <stefanr@...6.in-berlin.de>,
        Wolfram Sang <wsa@...nel.org>,
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        platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH 3/5] driver core: make struct device_type.uevent() take a
 const *

On Wed, Nov 23, 2022 at 05:49:36PM +0000, Matthew Wilcox wrote:
> On Wed, Nov 23, 2022 at 01:29:56PM -0400, Jason Gunthorpe wrote:
> > #define generic_container_of(in_type, in, out_type, out_member) \
> > 	_Generic(in,                                        \
> >                   const in_type *: ((const out_type *)container_of(in, out_type, out_member)),   \
> >                   in_type *: ((out_type *)container_of(in, out_type, out_member)) \
> > 		  )
> 
> There's a neat trick I found in seqlock.h:
> 
> #define generic_container_of(in_t, in, out_t, m)			\
> 	_Generic(*(in),							\
> 		const in_t: ((const out_t *)container_of(in, out_t, m)), \
> 		in_t: ((out_t *)container_of(in, out_type, m))	\
> 	)
>
> and now it fits in 80 columns ;-)

Aside from less letters, is their another benifit to using *(in) ?

Jason