linux-kernel - Re: [PATCH] spi: Fix warning about redefinition

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Message-ID: <20140806190412.GA5605@roeck-us.net>
Date:	Wed, 6 Aug 2014 12:04:12 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	David Wood <david@...ood.co.uk>
Cc:	Nick Krause <xerofoiffy@...il.com>,
	Mark Brown <broonie@...nel.org>,
	"open list:SPI SUBSYSTEM" <linux-spi@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	Richard Weinberger <richard.weinberger@...il.com>
Subject: Re: [PATCH] spi: Fix warning about redefinition

On Wed, Aug 06, 2014 at 08:53:41PM +0200, David Wood wrote:
> On Wed, 6 Aug 2014 11:33:28 -0700, Guenter Roeck wrote:
> > On Wed, Aug 06, 2014 at 07:19:54PM +0200, Richard Weinberger wrote:
> > > On Wed, Aug 6, 2014 at 6:55 PM, Nick Krause <xerofoiffy@...il.com> wrote:
> > > > Fix the following warnings about redefining READ and write
> > > >
> > > > drivers/spi/spi-omap-100k.c:73:0: warning: "WRITE" redefined [enabled by default]
> > > > include/linux/fs.h:193:0: note: this is the location of the previous definition
> > > > drivers/spi/spi-omap-100k.c:74:0: warning: "READ" redefined [enabled by default]
> > > > include/linux/fs.h:192:0: note: this is the location of the previous definition
> > > >
> > > > Signed-off-by: Nick Krause <xerofoiffy@...il.com>
> > > > ---
> > > >  drivers/spi/spi-omap-100k.c | 6 ++++++
> > > >  1 file changed, 6 insertions(+)
> > > >
> > > > diff --git a/drivers/spi/spi-omap-100k.c b/drivers/spi/spi-omap-100k.c
> > > > index 5e91858..eb8ae4e 100644
> > > > --- a/drivers/spi/spi-omap-100k.c
> > > > +++ b/drivers/spi/spi-omap-100k.c
> > > > @@ -70,6 +70,12 @@
> > > >  #define SPI_STATUS_WE                   (1UL << 1)
> > > >  #define SPI_STATUS_RD                   (1UL << 0)
> > > >
> > > > +#ifdef WRITE
> > > > +#undef WRITE
> > > > +#endif
> > > > +#ifdef READ
> > > > +#undef READ
> > > > +#endif
> > > >  #define WRITE 0
> > > >  #define READ  1
> > >
> > > Are these symbols even in use?
> > >
> >
> > It is always fun watching those patches flow by :-)
> > With the following patch:
> > diff --git a/drivers/spi/spi-omap-100k.c b/drivers/spi/spi-omap-100k.c
> > index 5e91858..f72ddfc 100644
> > --- a/drivers/spi/spi-omap-100k.c
> > +++ b/drivers/spi/spi-omap-100k.c
> > @@ -70,8 +70,8 @@
> >  #define SPI_STATUS_WE                   (1UL << 1)
> >  #define SPI_STATUS_RD                   (1UL << 0)
> > -#define WRITE 0
> > -#define READ  1
> > +#undef WRITE
> > +#undef READ
> > [ just to make sure that no existing defines are used instead of the new ones ]
> > When compiling the resulting code with W=1, I get:
> > drivers/spi/spi-omap-100k.c: In function 'spi100k_read_data':
> > drivers/spi/spi-omap-100k.c:148:6: warning: variable 'dataH' set but not used
> > [-Wunused-but-set-variable]
> > So, one might conclude that the defines are not used.
> > Guenter
> 
> There's also no need to have the undefines, as the READ is defined as

That was purely to ensure that there is no hidden use through a macro
defined elsewhere, not a suggestion for a real patch.

Guenter
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