linux-kernel - Re: [PATCH v2 4/5] drm/solomon: Move device info from ssd130x-i2c to the core driver

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Message-ID: <dd918de6-aaf3-a9d1-0504-4b6a3f3d4e9c@redhat.com>
Date:   Tue, 12 Apr 2022 14:47:49 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        David Airlie <airlied@...ux.ie>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Mark Brown <broonie@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Chen-Yu Tsai <wens@...nel.org>
Subject: Re: [PATCH v2 4/5] drm/solomon: Move device info from ssd130x-i2c to
 the core driver

On 4/12/22 13:22, Andy Shevchenko wrote:
> On Tue, Apr 12, 2022 at 02:21:08PM +0300, Andy Shevchenko wrote:
>> On Tue, Apr 12, 2022 at 10:07:02AM +0200, Javier Martinez Canillas wrote:
>>> On 4/12/22 09:23, Geert Uytterhoeven wrote:
>>>> On Mon, Apr 11, 2022 at 11:12 PM Javier Martinez Canillas
>>>> <javierm@...hat.com> wrote:
> 
> ...
> 
>>>>> -       ssd130x->device_info = device_get_match_data(dev);
>>>>> +
>>>>> +       variant = (enum ssd130x_variants)device_get_match_data(dev);
>>>>
>>>> (uintptr_t), to avoid a cast from pointer to integer of different
>>>> size warning.
>>>>
>>>
>>> Indeed. The kernel test robot reported the same.
>>
>> Not only because of this, but also with the non-NULL pointers I prefer the old
>> style without ugly castings.
>>
>> Instead, you may export the array (in the driver's namespace) and use
>> &info[ID] pointer for the specific device info.
> 
> Note that device_get_match_data() has no clue if the data is absent or
> data == (void *)0.
>

Yep, we could make the enum start at 1 and check for !variant but that's
something that will also be prevented by your suggestion to just use the
&info[ID] instead.

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat