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Date:   Thu, 1 Dec 2022 19:43:20 +0100
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Jason Gunthorpe <jgg@ziepe.ca>,
        Maximilian Luz <luzmaximilian@gmail.com>,
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Subject: Re: [PATCH 3/5] driver core: make struct device_type.uevent() take a
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On Wed, Nov 23, 2022 at 06:00:23PM +0000, Matthew Wilcox wrote:
> 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.

Ah, but your trick will not work, that blows up and will not build.  The
original one from Jason here does work.  _Generic is tricky...

thanks,

greg k-h