linux-kernel - Re: [PATCH v5 10/11] platform/x86: int3472: Pass tps68470_regulator_platform

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Date:   Tue, 2 Nov 2021 17:35:32 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Mark Gross <markgross@...nel.org>,
        Andy Shevchenko <andy@...radead.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Daniel Scally <djrscally@...il.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Len Brown <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        Kate Hsuan <hpa@...hat.com>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH v5 10/11] platform/x86: int3472: Pass
 tps68470_regulator_platform_data to the tps68470-regulator MFD-cell

Hi,

On 11/2/21 17:17, Sakari Ailus wrote:
> On Tue, Nov 02, 2021 at 03:59:41PM +0100, Hans de Goede wrote:
>> Hi,
>>
>> On 11/2/21 15:34, Andy Shevchenko wrote:
>>> On Tue, Nov 2, 2021 at 11:50 AM Hans de Goede <hdegoede@...hat.com> wrote:
>>>>
>>>> Pass tps68470_regulator_platform_data to the tps68470-regulator
>>>> MFD-cell, specifying the voltages of the various regulators and
>>>> tying the regulators to the sensor supplies so that sensors which use
>>>> the TPS68470 can find their regulators.
>>>>
>>>> Since the voltages and supply connections are board-specific, this
>>>> introduces a DMI matches int3472_tps68470_board_data struct which
>>>> contains the necessary per-board info.
>>>>
>>>> This per-board info also includes GPIO lookup information for the
>>>> sensor IO lines which may be connected to the tps68470 GPIOs.
>>>
>>> ...
>>>
>>>> +               board_data = int3472_tps68470_get_board_data(dev_name(&client->dev));
>>>> +               if (!board_data) {
>>>> +                       dev_err(&client->dev, "No board-data found for this laptop/tablet model\n");
>>>> +                       return -ENODEV;
>>>
>>> It's fine to use dev_err_probe() for known error codes.
>>>
>>>> +               }
>>>
>>> ...
>>>
>>>> +               cells[1].platform_data = (void *)board_data->tps68470_regulator_pdata;
>>>
>>> Do we need casting?
>>
>> Yes, the cast casts away a "const", the const is correct
>> since the data only ever gets read by the regulator driver,
>> but platform_data pointers are normally not const, so it
>> is either the cast, or loose the const on the definition
>> of the struct to which board_data->tps68470_regulator_pdata
>> points...
>>
>> So not good choice here really, only chosing between bad
>> options and I picked the lets do the cast "least worse"
>> option (at least to me). I'm open to changing this.
> 
> Maybe a comment explaining this briefly?

Yes, I was thinking the same myself, I'll add this for the
next version (which I expect to be the final version).

Regards,

Hans