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Date:   Wed, 23 Nov 2022 18:00:23 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Jason Gunthorpe <jgg@ziepe.ca>
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Subject: Re: [PATCH 3/5] driver core: make struct device_type.uevent() take a
 const *
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On Wed, Nov 23, 2022 at 01:55:42PM -0400, Jason Gunthorpe wrote:
> 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) ?

I don't think so.  It just looks nicer to me than putting the star in
each case.  If I'd thought of it, I would have done it to page_folio(),
but I won't change it now.