2017-07-11 22:15:44

by Gustavo A. R. Silva

Subject: [PATCH] gpio: altera-a10sr: 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
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 <[email protected]>
---
drivers/gpio/gpio-altera-a10sr.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpio/gpio-altera-a10sr.c b/drivers/gpio/gpio-altera-a10sr.c
index 16a8951..6b11f13 100644
--- a/drivers/gpio/gpio-altera-a10sr.c
+++ b/drivers/gpio/gpio-altera-a10sr.c
@@ -71,7 +71,7 @@ static int altr_a10sr_gpio_direction_output(struct gpio_chip *gc,
return -EINVAL;
}

-static struct gpio_chip altr_a10sr_gc = {
+static const struct gpio_chip altr_a10sr_gc = {
.label = "altr_a10sr_gpio",
.owner = THIS_MODULE,
.get = altr_a10sr_gpio_get,
--
2.5.0

2017-07-13 17:38:14

by Thor Thayer

Subject: Re: [PATCH] gpio: altera-a10sr: constify gpio_chip structure

On 07/11/2017 05:15 PM, Gustavo A. R. Silva wrote:
> This structure is only used to copy into another structure, so declare
> it as const.

<snip>

> Signed-off-by: Gustavo A. R. Silva <[email protected]>
> ---
> drivers/gpio/gpio-altera-a10sr.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpio-altera-a10sr.c b/drivers/gpio/gpio-altera-a10sr.c
> index 16a8951..6b11f13 100644
> --- a/drivers/gpio/gpio-altera-a10sr.c
> +++ b/drivers/gpio/gpio-altera-a10sr.c
> @@ -71,7 +71,7 @@ static int altr_a10sr_gpio_direction_output(struct gpio_chip *gc,
> return -EINVAL;
> }
>
> -static struct gpio_chip altr_a10sr_gc = {
> +static const struct gpio_chip altr_a10sr_gc = {
> .label = "altr_a10sr_gpio",
> .owner = THIS_MODULE,
> .get = altr_a10sr_gpio_get,
>
Reviewed-by: Thor Thayer <[email protected]>

2017-07-17 04:14:38

by Gustavo A. R. Silva

Subject: Re: [PATCH] gpio: altera-a10sr: constify gpio_chip structure

On 07/13/2017 12:41 PM, Thor Thayer wrote:
> On 07/11/2017 05:15 PM, Gustavo A. R. Silva wrote:
>> This structure is only used to copy into another structure, so declare
>> it as const.
>
> <snip>
>
>> Signed-off-by: Gustavo A. R. Silva <[email protected]>
>> ---
>> drivers/gpio/gpio-altera-a10sr.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpio/gpio-altera-a10sr.c
>> b/drivers/gpio/gpio-altera-a10sr.c
>> index 16a8951..6b11f13 100644
>> --- a/drivers/gpio/gpio-altera-a10sr.c
>> +++ b/drivers/gpio/gpio-altera-a10sr.c
>> @@ -71,7 +71,7 @@ static int altr_a10sr_gpio_direction_output(struct
>> gpio_chip *gc,
>> return -EINVAL;
>> }
>> -static struct gpio_chip altr_a10sr_gc = {
>> +static const struct gpio_chip altr_a10sr_gc = {
>> .label = "altr_a10sr_gpio",
>> .owner = THIS_MODULE,
>> .get = altr_a10sr_gpio_get,
>>
> Reviewed-by: Thor Thayer <[email protected]>

Thank you, Thor.

--
Gustavo A. R. Silva

2017-08-02 08:29:37

by Linus Walleij

Subject: Re: [PATCH] gpio: altera-a10sr: constify gpio_chip structure

On Wed, Jul 12, 2017 at 12:15 AM, 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
> 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 <[email protected]>

Patch applied with Thor's review tag.

Yours,
Linus Walleij