linux-kernel - Re: [PATCH 10/10] of/device: Don't NULLify match table in of_match_device() with CONFIG

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Date:   Thu, 17 Oct 2019 15:24:23 -0500
From:   Rob Herring <robh+dt@...nel.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Frank Rowand <frowand.list@...il.com>
Subject: Re: [PATCH 10/10] of/device: Don't NULLify match table in
 of_match_device() with CONFIG_OF=n

On Thu, Oct 17, 2019 at 12:48 PM Frank Rowand <frowand.list@...il.com> wrote:
>
> On 10/04/2019 16:43, Stephen Boyd wrote:
> > This effectively reverts 1db73ae39a97 ("of/device: Nullify match table
> > in of_match_device() for CONFIG_OF=n") because that commit makes it more
> > surprising to users of this API that the arguments may never be
> > referenced by any code. This is because the pre-processor will replace
> > the argument with NULL and then the match table will be left unreferenced
> > by any code but the compiler optimizer doesn't know to drop it. This can
> > lead to compilers warning that match tables are unused, when we really
> > want to pass the match table to the API but have the compiler see that
> > it's all inlined and not used and then drop the match table while
> > silencing the warning. We're being too smart here and not giving the
> > compiler the chance to do dead code elimination.
> >
> > Cc: Arnd Bergmann <arnd@...db.de>
> > Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
> > Cc: Rob Herring <robh+dt@...nel.org>
> > Cc: Frank Rowand <frowand.list@...il.com>
> > Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> > ---
> >
> > Please ack or pick for immediate merge so the last patch can be merged.

As this one is the last patch, I guess you don't want it picked up by itself.

It seems everyone has acked rather than applying. Do you want me to
take the series?

Rob

> >
> >  include/linux/of_device.h | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/include/linux/of_device.h b/include/linux/of_device.h
> > index 8d31e39dd564..3f8ca55bc693 100644
> > --- a/include/linux/of_device.h
> > +++ b/include/linux/of_device.h
> > @@ -93,13 +93,11 @@ static inline int of_device_uevent_modalias(struct device *dev,
> >
> >  static inline void of_device_node_put(struct device *dev) { }
> >
> > -static inline const struct of_device_id *__of_match_device(
> > +static inline const struct of_device_id *of_match_device(
> >               const struct of_device_id *matches, const struct device *dev)
> >  {
> >       return NULL;
> >  }
> > -#define of_match_device(matches, dev)        \
> > -     __of_match_device(of_match_ptr(matches), (dev))
> >
> >  static inline struct device_node *of_cpu_device_node_get(int cpu)
> >  {
> >
>
>
> Acked-by: Frank Rowand <frowand.list@...il.com>