linux-kernel - Re: [PATCH v2 6/6] of/device: Don't NULLify match table in of_match_device() with CONFIG

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Message-ID: <CAK8P3a3NinqnO0udFp21DyB1gdqa=vdavWgEpysfJFFs=V5hjA@mail.gmail.com>
Date:   Mon, 25 Jan 2021 10:46:31 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Rob Herring <robh@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v2 6/6] of/device: Don't NULLify match table in
 of_match_device() with CONFIG_OF=n

On Sat, Jan 23, 2021 at 4:44 AM Stephen Boyd <swboyd@...omium.org> 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.
>
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> Acked-by: Frank Rowand <frowand.list@...il.com>
> 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>

Reviewed-by: Arnd Bergmann <arnd@...db.de>