linux-kernel - Re: [PATCH] gpio: altera-a10sr: constify gpio

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Message-ID: <CACRpkdZ2rL64qiMrdBam5nQY9-6sayxfY6ppC0zm0fgQt3NHEQ@mail.gmail.com>
Date:   Wed, 2 Aug 2017 10:29:34 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Cc:     Thor Thayer <thor.thayer@...ux.intel.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpio: altera-a10sr: constify gpio_chip structure

On Wed, Jul 12, 2017 at 12:15 AM, Gustavo A. R. Silva
<garsilva@...eddedor.com> wrote:

> This structure is only used to copy into another structure, so declare
> it as const.
>
> This issue was detected using Coccinelle and the following semantic patch:
>
> @r disable optional_qualifier@
> identifier i;
> position p;
> @@
> static struct gpio_chip i@p = { ... };
>
> @ok@
> identifier r.i;
> expression e;
> position p;
> @@
> e = i@p;
>
> @bad@
> position p != {r.p,ok.p};
> identifier r.i;
> struct gpio_chip e;
> @@
> e@i@p
>
> @depends on !bad disable optional_qualifier@
> identifier r.i;
> @@
> static
> +const
>  struct gpio_chip i = { ... };
>
> In the following log you can see a significant difference in the code size
> and data segment, hence in the dec segment. This log is the output
> of the size command, before and after the code change:
>
> before:
>    text    data     bss     dec     hex filename
>    1954     600       0    2554     9fa drivers/gpio/gpio-altera-a10sr.o
>
> after:
>    text    data     bss     dec     hex filename
>    1655     512       0    2167     877 drivers/gpio/gpio-altera-a10sr.o
>
> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>

Patch applied with Thor's review tag.

Yours,
Linus Walleij