linux-kernel - Re: [PATCH -next v5 10/23] iio: imu: smi330: #undef field

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Message-ID: <20251109125956.106c9a1a@jic23-huawei>
Date: Sun, 9 Nov 2025 12:59:56 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
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Subject: Re: [PATCH -next v5 10/23] iio: imu: smi330: #undef
 field_{get,prep}() before definition

On Mon, 3 Nov 2025 11:09:36 +0100
Geert Uytterhoeven <geert@...ux-m68k.org> wrote:

> Hi Jonathan,
> 
> On Sun, 2 Nov 2025 at 11:43, Jonathan Cameron <jic23@...nel.org> wrote:
> > On Mon, 27 Oct 2025 19:41:44 +0100
> > Geert Uytterhoeven <geert+renesas@...der.be> wrote:
> >  
> > > Prepare for the advent of globally available common field_get() and
> > > field_prep() macros by undefining the symbols before defining local
> > > variants.  This prevents redefinition warnings from the C preprocessor
> > > when introducing the common macros later.
> > >
> > > Suggested-by: Yury Norov <yury.norov@...il.com>
> > > Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>  
> >
> > So this is going to make a mess of merging your series given this is
> > queued up for next merge window.
> >
> > I can pick this one up perhaps and we loop back to the replacement of
> > these in a future patch?  Or perhaps go instead with a rename
> > of these two which is probably nicer in the intermediate state than
> > undefs.  
> 
> Renaming would mean a lot of churn.
> Just picking up the #undef patch should be simple and safe? The
> removal of the underf and redef can be done in the next cycle.
> Thanks!

Only 1 call of each of these in the driver, so churn is small either way.

To avoid a bisection problem if your tree merges first I need to modify
this stuff in the original patch or leave it for Linus to deal with as
a merge conflict resolution which is mess I'd rather do without.

So I'll rebase now and rename these functions to have an smi330_ prefix.
Better to potentially cause people problems when I have 23 patches
on top of this (and hopefully no one is based on those yet) than when
I have many more.

So tweaked and pushed out a new version where this patch isn't needed.
We can move to your new code next cycle.

Jonathan



> 
> > > --- a/drivers/iio/imu/smi330/smi330_core.c
> > > +++ b/drivers/iio/imu/smi330/smi330_core.c
> > > @@ -68,7 +68,9 @@
> > >  #define SMI330_SOFT_RESET_DELAY 2000
> > >
> > >  /* Non-constant mask variant of FIELD_GET() and FIELD_PREP() */
> > > +#undef field_get
> > >  #define field_get(_mask, _reg) (((_reg) & (_mask)) >> (ffs(_mask) - 1))
> > > +#undef field_prep
> > >  #define field_prep(_mask, _val) (((_val) << (ffs(_mask) - 1)) & (_mask))
> > >
> > >  #define SMI330_ACCEL_CHANNEL(_axis) {                                        \  
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
>