linux-kernel - Re: [PATCH] pinctrl: bcm2835: constify gpio

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Date:   Wed, 2 Aug 2017 10:25:50 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        Eric Anholt <eric@...olt.net>,
        Stefan Wahren <stefan.wahren@...e.com>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        linux-rpi-kernel <linux-rpi-kernel@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pinctrl: bcm2835: constify gpio_chip structure

On Tue, Jul 11, 2017 at 8:03 PM, Gustavo A. R. Silva
<garsilva@...eddedor.com> wrote:

> This structure is only used to copy into other 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
>   18958    9000     128   28086    6db6 drivers/pinctrl/bcm/pinctrl-bcm2835.o
>
> after:
>    text    data     bss     dec     hex filename
>   18764    8912     128   27804    6c9c drivers/pinctrl/bcm/pinctrl-bcm2835.o
>
> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>

Patch applied with Eric's ACK.

Yours,
Linus Walleij