linux-kernel - Re: [PATCH] Make gpiochip label const

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Message-ID: <20080820083943.GA24244@doriath.ww600.siemens.net>
Date:	Wed, 20 Aug 2008 12:39:43 +0400
From:	Dmitry Baryshkov <dbaryshkov@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	david-b@...bell.net, linux-kernel@...r.kernel.org,
	dbrownell@...rs.sourceforge.net
Subject: Re: [PATCH] Make gpiochip label const

On Tue, Aug 19, 2008 at 11:28:28AM -0700, Andrew Morton wrote:
> On Tue, 19 Aug 2008 15:13:47 +0400
> Dmitry <dbaryshkov@...il.com> wrote:
> 
> > 2008/8/19 Andrew Morton <akpm@...ux-foundation.org>:
> > > On Sun, 17 Aug 2008 23:00:35 +0400 Dmitry Baryshkov <dbaryshkov@...il.com> wrote:
> > >
> > >> On Tue, Aug 12, 2008 at 03:06:19PM -0700, David Brownell wrote:
> > >> > > From dbaryshkov@...il.com  Tue Aug 12 13:54:29 2008
> > >> > > From: Dmitry Baryshkov <dbaryshkov@...il.com>
> > >> > > To: linux-kernel@...r.kernel.org
> > >> > > Cc: Dmitry Baryshkov <dbaryshkov@...il.com>,
> > >> > >   David Brownell <dbrownell@...rs.sourceforge.net>
> > >> > > Subject: [PATCH] Make gpiochip label const
> > >> > > Date: Wed, 13 Aug 2008 00:39:48 +0400
> > >> > >
> > >> > > Mark gpiochip label as a const char pointer.
> > >> > >
> > >> > > Signed-off-by: Dmitry Baryshkov <dbaryshkov@...il.com>
> > >> > > Cc: David Brownell <dbrownell@...rs.sourceforge.net>
> > >> >
> > >> > Acked-By: David Brownell <dbrownell@...rs.sourceforge.net>
> > >> >
> > >>
> > >> Sorry to disturb, but will this make into 2.6.27-rc? Thanks.
> > >>
> > >
> > > Ordinarily it would not.  Is there some reason why you think it should?
> > >
> > 
> > It fixes lots of warnings (one per each instance of code filling the gpio chip)
> 
> 
> That should have been in the changelog!
> 
> When fixing warnings or compilations errors, the compiler output should
> also be in the changelog.

Thanks for the tip. It it written somewhere?

> I don't recall seeing such warnings and I cannot make them happen with
> drivers/gpio/gpiolib.c or with drivers/gpio/max732x.c or with
> drivers/gpio/pca953x.c.  So we still don't know what this patch
> does :(

Because both mentioned drivers set gpiochip->label to non-const string.
You can check arch/arm/common/scoop.c for example of driver showing
different behaviour:

  CHECK   /home/lumag/tosa-tree/arch/arm/common/scoop.c
/home/lumag/tosa-tree/arch/arm/common/scoop.c:250:22: warning: incorrect type in assignment (different modifiers)
/home/lumag/tosa-tree/arch/arm/common/scoop.c:250:22:    expected char *label
/home/lumag/tosa-tree/arch/arm/common/scoop.c:250:22:    got char const *
  CC      arch/arm/common/scoop.o
/home/lumag/tosa-tree/arch/arm/common/scoop.c: In function ‘scoop_probe’:
/home/lumag/tosa-tree/arch/arm/common/scoop.c:250: warning: assignment discards qualifiers from pointer target type

> 
> > and is pretty much small to honour inclusion IMO
> 
> Well sure it's small.  But converting things to `const' carries a
> fairly high risk of adding new warnings or breaking the build.

Should we stage it into linux-next?

-- 
With best wishes
Dmitry

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