linux-kernel - Re: [PATCH v3 09/17] m68k: io: implement dummy relaxed accessor macros for writes

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Date:	Thu, 25 Sep 2014 10:33:09 +0100
From:	Will Deacon <will.deacon@....com>
To:	Greg Ungerer <gerg@...inux.org>
Cc:	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
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	"geert@...ux-m68k.org" <geert@...ux-m68k.org>,
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Subject: Re: [PATCH v3 09/17] m68k: io: implement dummy relaxed accessor
 macros for writes

On Thu, Sep 25, 2014 at 02:05:43AM +0100, Greg Ungerer wrote:
> Hi Will

Hi Greg,

Thanks for taking a look.

> On 25/09/14 03:17, Will Deacon wrote:
> > write{b,w,l}_relaxed are implemented by some architectures in order to
> > permit memory-mapped I/O accesses with weaker barrier semantics than the
> > non-relaxed variants.
> > 
> > This patch adds dummy macros for the write accessors to m68k, in the
> > same vein as the dummy definitions for the relaxed read accessors.
> > Additionally, the existing relaxed read accessors are moved into
> > asm/io.h, so that they can be used by m68k targets with an MMU.
> > 
> > Acked-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> > Signed-off-by: Will Deacon <will.deacon@....com>
> > ---
> >  arch/m68k/include/asm/io.h    | 8 ++++++++
> >  arch/m68k/include/asm/io_no.h | 4 ----
> >  2 files changed, 8 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/m68k/include/asm/io.h b/arch/m68k/include/asm/io.h
> > index c70cc9155003..bccd5a914eb6 100644
> > --- a/arch/m68k/include/asm/io.h
> > +++ b/arch/m68k/include/asm/io.h
> > @@ -3,3 +3,11 @@
> >  #else
> >  #include <asm/io_mm.h>
> >  #endif
> > +
> > +#define readb_relaxed(addr)	readb(addr)
> > +#define readw_relaxed(addr)	readw(addr)
> > +#define readl_relaxed(addr)	readl(addr)
> > +
> > +#define writeb_relaxed(b, addr)	writeb(b, addr)
> > +#define writew_relaxed(b, addr)	writew(b, addr)
> > +#define writel_relaxed(b, addr)	writel(b, addr)
> 
> Putting them here means they won't have any multiple include protection
> (there is no "#ifndef _IO_H" around them). Doesn't seem to lead to
> any problems in practice. Just flagging it...

That's easy enough to fix, and actually, we should have __KERNEL__ checks
here too. Fixup below.

Will

--->8

diff --git a/arch/m68k/include/asm/io.h b/arch/m68k/include/asm/io.h
index bccd5a914eb6..ded201916560 100644
--- a/arch/m68k/include/asm/io.h
+++ b/arch/m68k/include/asm/io.h
@@ -1,9 +1,14 @@
+#ifndef _M68K_IO_H
+#define _M68K_IO_H
+
 #ifdef __uClinux__
 #include <asm/io_no.h>
 #else
 #include <asm/io_mm.h>
 #endif
 
+#ifdef __KERNEL__
+
 #define readb_relaxed(addr)    readb(addr)
 #define readw_relaxed(addr)    readw(addr)
 #define readl_relaxed(addr)    readl(addr)
@@ -11,3 +16,6 @@
 #define writeb_relaxed(b, addr)        writeb(b, addr)
 #define writew_relaxed(b, addr)        writew(b, addr)
 #define writel_relaxed(b, addr)        writel(b, addr)
+
+#endif /* __KERNEL__ */
+#endif /* _M68K_IO_H */
--
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