linux-kernel - Re: [PATCH v5 5/5] pinctrl: s32: separate const device data from struct s32_pinctrl_soc

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Date:   Wed, 29 Mar 2023 12:25:54 +0800
From:   Chester Lin <clin@...e.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        NXP S32 Linux Team <s32@....com>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Ghennadi Procopciuc <Ghennadi.Procopciuc@....nxp.com>,
        Andrei Stefanescu <andrei.stefanescu@....com>,
        Radu Pirea <radu-nicolae.pirea@....com>,
        Andreas Färber <afaerber@...e.de>,
        Matthias Brugger <mbrugger@...e.com>
Subject: Re: [PATCH v5 5/5] pinctrl: s32: separate const device data from
 struct s32_pinctrl_soc_info

Hi Linus and Andy,

On Mon, Mar 27, 2023 at 11:39:18PM +0200, Linus Walleij wrote:
> On Mon, Mar 27, 2023 at 1:59 PM Andy Shevchenko
> <andy.shevchenko@...il.com> wrote:
> > On Mon, Mar 27, 2023 at 9:28 AM Chester Lin <clin@...e.com> wrote:
> > >
> > > The .data field in struct of_device_id is used as a const member so it's
> > > inappropriate to attach struct s32_pinctrl_soc_info with of_device_id
> > > because some members in s32_pinctrl_soc_info need to be filled by
> > > pinctrl-s32cc at runtime.
> > >
> > > For this reason, struct s32_pinctrl_soc_info must be allocated in
> > > pinctrl-s32cc and then create a new struct s32_pinctrl_soc_data in order
> > > to represent const .data in of_device_id. To combine these two structures,
> > > a s32_pinctrl_soc_data pointer is introduced in s32_pinctrl_soc_info.
> > >
> > > Besides, use of_device_get_match_data() instead of of_match_device() since
> > > the driver only needs to retrieve the .data from of_device_id.
> >
> > ...
> >
> > > -static struct s32_pinctrl_soc_info s32_pinctrl_info = {
> > > +static struct s32_pinctrl_soc_data s32_pinctrl_data = {
> >
> > I'm wondering why it's not const.
> >
> > But don't resend too quickly, let's wait for Linus to comment on this
> > and other stuff. It might be that he can amend this when applying.
> 
> I don't dare to add const here given the compiler warnings it
> can easily spawn.
> 
> Chester can you investigate if these can be static const?
> 
> You would only need to resend this patch 5/5 because I applied
> all the others to lower your patch stack.
> 
> Thanks for fixing!
> Yours,
> Linus Walleij

Thanks for reviewing this patch and Andy's suggestion looks good to me. The
s32_pinctrl_data should be const as well since the 'data' pointer in
of_device_id is declared as const.

Anyway, I have resent a revised 5/5 under the same mail thread:
https://lore.kernel.org/all/20230329041630.8011-1-clin@suse.com/T/#u

It can be compiled by the following two gcc versions without a warning on
drivers/pinctrl/nxp

- aarch64-native:
  - gcc version 7.5.0 (SUSE Linux)  <aarch64-native>

- cross-compilation on x86-64
  - gcc version 13.0.1 20230127 (experimental) [revision ca8fb0096713a8477614ef874f16ba5bf16c48bc] (SUSE Linux)

Thanks!

Regards,
Chester