2017-07-11 21:35:25

by Gustavo A. R. Silva

Subject: [PATCH] pinctrl: coh901: constify gpio_chip structure

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
12775 3696 64 16535 4097 drivers/pinctrl/pinctrl-coh901.o

after:
bss dec hex filename
12440 3640 64 16144 3f10 drivers/pinctrl/pinctrl-coh901.o

Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
drivers/pinctrl/pinctrl-coh901.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pinctrl/pinctrl-coh901.c b/drivers/pinctrl/pinctrl-coh901.c
index 741b39e..ac155e7 100644
--- a/drivers/pinctrl/pinctrl-coh901.c
+++ b/drivers/pinctrl/pinctrl-coh901.c
@@ -387,7 +387,7 @@ int u300_gpio_config_set(struct gpio_chip *chip, unsigned offset,
return 0;
}

-static struct gpio_chip u300_gpio_chip = {
+static const struct gpio_chip u300_gpio_chip = {
.label = "u300-gpio-chip",
.owner = THIS_MODULE,
.request = gpiochip_generic_request,
--
2.5.0

2017-08-01 08:00:01

by Linus Walleij

Subject: Re: [PATCH] pinctrl: coh901: constify gpio_chip structure

On Tue, Jul 11, 2017 at 11:35 PM, Gustavo A. R. Silva
<[email protected]> 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
> 12775 3696 64 16535 4097 drivers/pinctrl/pinctrl-coh901.o
>
> after:
> bss dec hex filename
> 12440 3640 64 16144 3f10 drivers/pinctrl/pinctrl-coh901.o
>
> Signed-off-by: Gustavo A. R. Silva <[email protected]>

Patch applied.

Yours,
Linus Walleij