linux-kernel - Re: [PATCH v2 1/1] iio: humidity: hdc100x: add manufacturer and device ID cehck

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Message-ID: <CAHp75VdjvJRwzPLLdMji+_m2tQY4JLBcNwt-QFkDJTyGFUOdKg@mail.gmail.com>
Date:   Wed, 27 Jul 2022 13:56:43 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Potin Lai <potin.lai.pt@...il.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Patrick Williams <patrick@...cx.xyz>,
        Potin Lai <potin.lai@...ntatw.com>,
        linux-iio <linux-iio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/1] iio: humidity: hdc100x: add manufacturer and
 device ID cehck

On Wed, Jul 27, 2022 at 12:42 PM Potin Lai <potin.lai.pt@...il.com> wrote:
> On 7/27/22 18:00, Andy Shevchenko wrote:
> > On Wed, Jul 27, 2022 at 8:46 AM Potin Lai <potin.lai.pt@...il.com> wrote:

...

> >> +       data = device_get_match_data(&client->dev);
> >> +       if (data) {
> > This check is redundant. Too much protective programming. Just oblige
> > that matched ID has to always have an associated data.
> Is it guaranteed that device_get_match_data will not return NULL? I find some examples in other drivers, all of them have a check on returned data.

No, but as I said you may guarantee that by obliging developers not to
shoot in their feet.

> Will it be more appropriate if I move device_get_match_data to probe function, and return EINVAL when we get a NULL pointer from device_get_match_data?

Why is this check needed? We do not like dead code.

> >> +               if (!data->support_mfr_check)
> >> +                       return true;
> >> +       }

-- 
With Best Regards,
Andy Shevchenko