linux-kernel - Re: [PATCH v2] i2c: Use u8 type in i2c transfer calls

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Message-ID: <CAHp75Vd6yEctJoNT6TpJ1+h4ZQckyLsaUSeSCV4MHqg+LUDkcg@mail.gmail.com>
Date:   Wed, 3 Aug 2022 18:46:48 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Jason Gerecke <killertofu@...il.com>
Cc:     linux-i2c <linux-i2c@...r.kernel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Wolfram Sang <wsa-dev@...g-engineering.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ping Cheng <pinglinux@...il.com>,
        "Tobita, Tatsunosuke" <tatsunosuke.tobita@...om.com>,
        Jason Gerecke <jason.gerecke@...om.com>,
        Ping Cheng <ping.cheng@...om.com>
Subject: Re: [PATCH v2] i2c: Use u8 type in i2c transfer calls

On Wed, Aug 3, 2022 at 4:59 PM Jason Gerecke <killertofu@...il.com> wrote:
>
> The 'i2c_transfer_buffer_flags' function (and related inlines) defines its

We refer to the functions like func() (without any quotes as well).

> 'buf' argument to be of type 'char*'. This is a poor choice of type given

char *

> that most callers actually pass a 'u8*' and that the function itself ends

most of the callers

u8 *

> up just storing the variable to a 'u8*'-typed member of 'struct i2c_msg'

u8 *

> anyway.
>
> Changing the type of the 'buf' argument to 'u8*' vastly reduces the number

u8 *

> of (admittedly usually-silent) Wpointer-sign warnings that are generated

-Wpointer-sign or replace with simple English words.

> as the types get needlessly juggled back and forth.
>
> At the same time, update the max1363 driver to match the new interface so
> we don't introduce a new Wincompatible-function-pointer-types warning.

-Wincompatible-function-pointer-types

...

> Changes in v2:
>   - Added modifications to the max1363 driver required to avoid warnings

Have you really checked _all_ callers of APIs that you have changed here?

For example, drivers/media/usb/em28xx/em28xx-input.c still uses
unsigned char for i2c_master_recv().

I believe you need to create a coccinelle script and run it over the
kernel source tree and then create a patch out of it.

-- 
With Best Regards,
Andy Shevchenko