linux-kernel - Re: [PATCH 1/2] i2c: i2c-bcm-iproc: fix -Wvoid-pointer-to-enum-cast warning

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Date:   Thu, 10 Aug 2023 07:44:52 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Andi Shyti <andi.shyti@...nel.org>
Cc:     Justin Stitt <justinstitt@...gle.com>, Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>, linux-i2c@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH 1/2] i2c: i2c-bcm-iproc: fix -Wvoid-pointer-to-enum-cast
 warning

Hi Andi,

On Thu, Aug 10, 2023 at 10:56:32AM +0200, Andi Shyti wrote:
> Hi Justin,
> 
> > @@ -1036,7 +1036,7 @@ static int bcm_iproc_i2c_probe(struct platform_device *pdev)
> >  	platform_set_drvdata(pdev, iproc_i2c);
> >  	iproc_i2c->device = &pdev->dev;
> >  	iproc_i2c->type =
> > -		(enum bcm_iproc_i2c_type)of_device_get_match_data(&pdev->dev);
> > +		(unsigned long) of_device_get_match_data(&pdev->dev);
> 
> I think this should be uintptr_t, as defined in types.h:
> 
>     typedef unsigned long uintptr_t;

Yes, that is a valid comment, although I will say that I have seen some
developers/maintainers prefer 'unsigned long' over 'uintptr_t', so it is
really a crapshoot which one to pick :)

> (I'm a bit puzzled to see a void *data cast to a 0/1 value.)

It is an odd pattern but as far as I understand it, the kernel uses it a
lot to pass platform specific data around (just grepping for
'.data = (void *)' shows a lot of instances.

Cheers,
Nathan