linux-kernel - Re: [PATCH 1/1] i2c: at91: constify at91_twi

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Date:   Sun, 2 Jul 2023 12:40:05 +0200
From:   Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:     Andi Shyti <andi.shyti@...nel.org>
Cc:     Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] i2c: at91: constify at91_twi_pdata

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.

-- 
Michał Mirosław