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

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Date:   Wed, 12 Jul 2017 07:03:29 +0000
From:   Patrice CHOTARD <patrice.chotard@...com>
To:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>,
        Linus Walleij <linus.walleij@...aro.org>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pinctrl: st: constify gpio_chip structure

Hi Gustavo

On 07/11/2017 08:15 PM, Gustavo A. R. Silva 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
>    21671    3632     128   25431    6357 drivers/pinctrl/pinctrl-st.o
> 
> after:
>     text    data     bss     dec     hex filename
>    21366    3576     128   25070    61ee drivers/pinctrl/pinctrl-st.o
> 
> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
> ---
>   drivers/pinctrl/pinctrl-st.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pinctrl/pinctrl-st.c b/drivers/pinctrl/pinctrl-st.c
> index 3ae8066..5d4789d 100644
> --- a/drivers/pinctrl/pinctrl-st.c
> +++ b/drivers/pinctrl/pinctrl-st.c
> @@ -1442,7 +1442,7 @@ static void st_gpio_irqmux_handler(struct irq_desc *desc)
>   	chained_irq_exit(chip, desc);
>   }
>   
> -static struct gpio_chip st_gpio_template = {
> +static const struct gpio_chip st_gpio_template = {
>   	.request		= gpiochip_generic_request,
>   	.free			= gpiochip_generic_free,
>   	.get			= st_gpio_get,
> 

Acked-by: Patrice Chotard <patrice.chotard@...com>

Thanks