linux-kernel - Re: [PATCH v2 1/2] pinctrl: ocelot: Fix pincfg for lan966x

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Date:   Mon, 11 Jul 2022 10:31:50 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Horatiu Vultur <horatiu.vultur@...rochip.com>
Cc:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        kavyasree.kotagiri@...rochip.com,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Colin Foster <colin.foster@...advantage.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>,
        Michael Walle <michael@...le.cc>
Subject: Re: [PATCH v2 1/2] pinctrl: ocelot: Fix pincfg for lan966x

On Mon, Jul 11, 2022 at 8:45 AM Horatiu Vultur
<horatiu.vultur@...rochip.com> wrote:
> The 07/08/2022 23:58, Andy Shevchenko wrote:
> > On Fri, Jul 8, 2022 at 10:10 PM Horatiu Vultur
> > <horatiu.vultur@...rochip.com> wrote:

Please, remove unneeded context when replying!

...

> > > +       struct ocelot_match_data *data;
> >
> > Any specific reason why this is not const?
> >
> > > +       data = (struct ocelot_match_data *)device_get_match_data(dev);
> >
> > And here you drop the qualifier...
> >
> > I would recommend making it const and dropping the cast completely.
>
> If I make this const, but then few lines after I will get the following
> warnings:
>
> drivers/pinctrl/pinctrl-ocelot.c:1983:13: warning: assignment discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
> 1983 |  info->desc = &data->desc;
>      |             ^
> drivers/pinctrl/pinctrl-ocelot.c:1984:20: warning: assignment discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
> 1984 |  info->pincfg_data = &data->pincfg_data;
>      |                    ^
>
> Of course I can make also info->desc and info->pincfg_data const but
> then I will get the following warning:
>
> drivers/pinctrl/pinctrl-ocelot.c: In function ‘ocelot_pinctrl_register’:
> drivers/pinctrl/pinctrl-ocelot.c:1723:53: warning: passing argument 2 of ‘devm_pinctrl_register’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
> 1723 |  info->pctl = devm_pinctrl_register(&pdev->dev, info->desc, info);
>      |                                                 ~~~~^~~~~~
> In file included from include/linux/gpio/driver.h:10,
>                  from drivers/pinctrl/pinctrl-ocelot.c:10:
>                       include/linux/pinctrl/pinctrl.h:166:26: note: expected ‘struct pinctrl_desc *’ but argument is of type ‘const struct pinctrl_desc *’
> 166 |     struct pinctrl_desc *pctldesc,
>     |     ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
>
> > > +       if (!data)
> > > +               return -EINVAL;

This is not good. Any chances to make it const?

One way is to copy data in a newly allocated buffer (devm_kmemdup() for that).

-- 
With Best Regards,
Andy Shevchenko