linux-kernel - Re: [PATCH v3 00/17] Cross-architecture definitions of relaxed MMIO accessors

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Message-Id: <201409252117.19754.arnd@arndb.de>
Date:	Thu, 25 Sep 2014 21:17:19 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Daniel Thompson <daniel.thompson@...aro.org>
Cc:	Will Deacon <will.deacon@....com>,
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Subject: Re: [PATCH v3 00/17] Cross-architecture definitions of relaxed MMIO accessors

On Thursday 25 September 2014, Daniel Thompson wrote:
> > +
> > +#ifndef readq_relaxed
> > +#define readq_relaxed readq
> > +#endif
> 
> Not really sure if it matters but this gives a rather surprising
> behaviour to #ifdef readq_relaxed given that readq may not be defined.
> 

It was intentional. I could have written this as

#if !defined(readq_relaxed) && defined(readq)

but the effect would be almost the same, and the version I picked looks
simpler. Note that 32-bit architectures could provide readq, it's just
the generic code that doesn't, because most you typically don't get
atomic 64-bit accesses from dereferencing a 64-bit pointer as the
generic readq() function does.

	Arnd
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