linux-kernel - Re: [PATCH v7 1/3] devres: provide devm

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Message-ID: <20200818171046.GU1891694@smile.fi.intel.com>
Date:   Tue, 18 Aug 2020 20:10:46 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Michal Simek <michal.simek@...inx.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        linux-iio <linux-iio@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v7 1/3] devres: provide devm_krealloc()

On Tue, Aug 18, 2020 at 06:27:12PM +0200, Bartosz Golaszewski wrote:
> On Tue, Aug 18, 2020 at 10:40 AM Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> wrote:
> >
> > On Mon, Aug 17, 2020 at 10:02:05PM +0200, Bartosz Golaszewski wrote:
> > > On Mon, Aug 17, 2020 at 7:43 PM Andy Shevchenko
> > > <andriy.shevchenko@...ux.intel.com> wrote:
> > > > On Mon, Aug 17, 2020 at 07:05:33PM +0200, Bartosz Golaszewski wrote:
> > > > > From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> >
> > ...
> >
> > > > > +static struct devres *to_devres(void *data)
> > > > > +{
> > > > > +     return (struct devres *)((u8 *)data - ALIGN(sizeof(struct devres),
> > > > > +                                                 ARCH_KMALLOC_MINALIGN));
> > > >
> > > > Do you really need both explicit castings?
> > > >
> > >
> > > Yeah, we can probably drop the (struct devres *) here.
> >
> > void * -> u8 * here is also not needed, it is considered byte access IIRC.
> >
> 
> Actually it turns out that while we don't need the (void *) -> (u8 *)
> casting, we must cast to (struct devres *) or the following error is
> produced:
> 
> drivers/base/devres.c: In function ‘to_devres’:
> drivers/base/devres.c:41:21: error: returning ‘u8 *’ {aka ‘unsigned
> char *’} from a function with incompatible return type ‘struct devres
> *’ [-Werror=incompatible-pointer-types]
>   return ((u8 *)data - ALIGN(sizeof(struct devres),
>          ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>         ARCH_KMALLOC_MINALIGN));
>         ~~~~~~~~~~~~~~~~~~~~~~~

Of course, you have to drop u8 * casting as well.

-- 
With Best Regards,
Andy Shevchenko