[1/1] i2c: at91: constify at91_twi_pdata

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
---
 drivers/i2c/busses/i2c-at91-core.c   | 24 ++++++++++++------------
 drivers/i2c/busses/i2c-at91-master.c |  4 ++--
 drivers/i2c/busses/i2c-at91.h        |  2 +-
 3 files changed, 15 insertions(+), 15 deletions(-)

Hi Michal,

[...]

> -static struct at91_twi_pdata *at91_twi_get_driver_data(
> +static const struct at91_twi_pdata *at91_twi_get_driver_data(
>  					struct platform_device *pdev)
>  {
>  	if (pdev->dev.of_node) {
> @@ -189,9 +189,9 @@ static struct at91_twi_pdata *at91_twi_get_driver_data(
>  		match = of_match_node(atmel_twi_dt_ids, pdev->dev.of_node);
>  		if (!match)
>  			return NULL;
> -		return (struct at91_twi_pdata *)match->data;
> +		return match->data;
>  	}
> -	return (struct at91_twi_pdata *) platform_get_device_id(pdev)->driver_data;
> +	return (const void *) platform_get_device_id(pdev)->driver_data;

the const's always confuse me... do you get an error here? Is
this cast really needed?

Andi

On Fri, Jun 30, 2023 at 12:38:25AM +0200, Andi Shyti wrote:
> Hi Michal,
> 
> [...]
> 
> > -static struct at91_twi_pdata *at91_twi_get_driver_data(
> > +static const struct at91_twi_pdata *at91_twi_get_driver_data(
> >  					struct platform_device *pdev)
> >  {
> >  	if (pdev->dev.of_node) {
> > @@ -189,9 +189,9 @@ static struct at91_twi_pdata *at91_twi_get_driver_data(
> >  		match = of_match_node(atmel_twi_dt_ids, pdev->dev.of_node);
> >  		if (!match)
> >  			return NULL;
> > -		return (struct at91_twi_pdata *)match->data;
> > +		return match->data;
> >  	}
> > -	return (struct at91_twi_pdata *) platform_get_device_id(pdev)->driver_data;
> > +	return (const void *) platform_get_device_id(pdev)->driver_data;
> 
> the const's always confuse me... do you get an error here? Is
> this cast really needed?

platform_device_id.driver_data is an ulong, not a void pointer. So, the
cast is needed. It could be just (void *), but I think it's better to
document the constness in the code.

On 30/06/2023 00:38, Andi Shyti wrote:
> Hi Michal,
> 
> [...]
> 
>> -static struct at91_twi_pdata *at91_twi_get_driver_data(
>> +static const struct at91_twi_pdata *at91_twi_get_driver_data(
>>  					struct platform_device *pdev)
>>  {
>>  	if (pdev->dev.of_node) {
>> @@ -189,9 +189,9 @@ static struct at91_twi_pdata *at91_twi_get_driver_data(
>>  		match = of_match_node(atmel_twi_dt_ids, pdev->dev.of_node);
>>  		if (!match)
>>  			return NULL;
>> -		return (struct at91_twi_pdata *)match->data;
>> +		return match->data;
>>  	}
>> -	return (struct at91_twi_pdata *) platform_get_device_id(pdev)->driver_data;
>> +	return (const void *) platform_get_device_id(pdev)->driver_data;
> 
> the const's always confuse me... do you get an error here? Is
> this cast really needed?

I think this change is not necessary and actually should not matter. See
for example drivers/tty/serial/samsung_tty.c after my refactorings in
commit 3aec40096550 ("tty: serial: samsung: reduce number of casts").

Best regards,
Krzysztof

On Mon, Jul 03, 2023 at 08:23:30PM +0200, Krzysztof Kozlowski wrote:
> On 30/06/2023 00:38, Andi Shyti wrote:
> > Hi Michal,
> >> -static struct at91_twi_pdata *at91_twi_get_driver_data(
> >> +static const struct at91_twi_pdata *at91_twi_get_driver_data(
> >>  					struct platform_device *pdev)
> >>  {
> >>  	if (pdev->dev.of_node) {
> >> @@ -189,9 +189,9 @@ static struct at91_twi_pdata *at91_twi_get_driver_data(
> >>  		match = of_match_node(atmel_twi_dt_ids, pdev->dev.of_node);
> >>  		if (!match)
> >>  			return NULL;
> >> -		return (struct at91_twi_pdata *)match->data;
> >> +		return match->data;
> >>  	}
> >> -	return (struct at91_twi_pdata *) platform_get_device_id(pdev)->driver_data;
> >> +	return (const void *) platform_get_device_id(pdev)->driver_data;
> > 
> > the const's always confuse me... do you get an error here? Is
> > this cast really needed?
> 
> I think this change is not necessary and actually should not matter. See
> for example drivers/tty/serial/samsung_tty.c after my refactorings in
> commit 3aec40096550 ("tty: serial: samsung: reduce number of casts").

I added this two fragments to avoid having suggesting that the pdata might
not be in a read-only segment.  For the compiler it doesn't matter -- the
pointer is cast to const on return.

Best Regards
Michał Mirosław