[PATCH] pinctrl: vt8500: wmt: constify gpio_chip structure

[PATCH] pinctrl: vt8500: wmt: constify gpio_chip structure

[Gustavo A. R. Silva]

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
   7754    2328       0   10082    2762 drivers/pinctrl/vt8500/pinctrl-wmt.o

after:
   text    data     bss     dec     hex filename
   7472    2272       0    9744    2610 drivers/pinctrl/vt8500/pinctrl-wmt.o

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
---
 drivers/pinctrl/vt8500/pinctrl-wmt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pinctrl/vt8500/pinctrl-wmt.c b/drivers/pinctrl/vt8500/pinctrl-wmt.c
index c207e60..974e646 100644
--- a/drivers/pinctrl/vt8500/pinctrl-wmt.c
+++ b/drivers/pinctrl/vt8500/pinctrl-wmt.c
@@ -546,7 +546,7 @@ static int wmt_gpio_direction_output(struct gpio_chip *chip, unsigned offset,
 	return pinctrl_gpio_direction_output(chip->base + offset);
 }
 
-static struct gpio_chip wmt_gpio_chip = {
+static const struct gpio_chip wmt_gpio_chip = {
 	.label = "gpio-wmt",
 	.owner = THIS_MODULE,
 	.request = gpiochip_generic_request,
-- 
2.5.0

Re: [PATCH] pinctrl: vt8500: wmt: constify gpio_chip structure

[Linus Walleij]

On Tue, Jul 11, 2017 at 8:28 PM, Gustavo A. R. Silva
<garsilva@embeddedor.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
>    7754    2328       0   10082    2762 drivers/pinctrl/vt8500/pinctrl-wmt.o
>
> after:
>    text    data     bss     dec     hex filename
>    7472    2272       0    9744    2610 drivers/pinctrl/vt8500/pinctrl-wmt.o
>
> Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>

Patch applied.

Yours,
Linus Walleij