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Date:   Thu, 30 Mar 2023 10:04:53 +0200
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Subject: Re: [PATCH v6 5/5] mfd: max77541: Add ADI MAX77541/MAX77540 PMIC
 Support
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To:     Lee Jones <lee@kernel.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc:     "Sahin, Okan" <Okan.Sahin@analog.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Jonathan Cameron <jic23@kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Cosmin Tanislav <demonsingur@gmail.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Caleb Connolly <caleb.connolly@linaro.org>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
        "Bolboaca, Ramona" <Ramona.Bolboaca@analog.com>,
        ChiYuan Huang <cy_huang@richtek.com>,
        "Tilki, Ibrahim" <Ibrahim.Tilki@analog.com>,
        William Breathitt Gray <william.gray@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>,
        ChiaEn Wu <chiaen_wu@richtek.com>,
        Haibo Chen <haibo.chen@nxp.com>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>
References: <20230307112835.81886-1-okan.sahin@analog.com>
 <20230307112835.81886-6-okan.sahin@analog.com>
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From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <20230329150605.GW2673958@google.com>
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On 29/03/2023 17:06, Lee Jones wrote:
> On Wed, 29 Mar 2023, Lee Jones wrote:
> 
>> On Wed, 29 Mar 2023, Andy Shevchenko wrote:
>>
>>> On Wed, Mar 29, 2023 at 03:36:15PM +0100, Lee Jones wrote:
>>>> On Tue, 28 Mar 2023, Sahin, Okan wrote:
>>>>>> On Wed, 15 Mar 2023, Lee Jones wrote:
>>>>>>> On Tue, 07 Mar 2023, Okan Sahin wrote:
>>>
>>> ...
>>>
>>>>> +static const struct i2c_device_id max77541_i2c_id[] = {
>>>>> +	{ "max77540", (kernel_ulong_t)&chip[MAX77540] },
>>>>> +	{ "max77541", (kernel_ulong_t)&chip[MAX77541] },
>>>>
>>>> Just 'MAX77540' is fine.
>>>
>>> I tend to disagree.
>>>
>>> There is an error prone approach esp. when we talk with some functions
>>> that unifies OF/ACPI driver data retrieval with legacy ID tables.
>>> In such a case the 0 from enum is hard to distinguish from NULL when
>>> the driver data is not set or not found. On top of that the simple integer
>>> in the legacy driver data will require additional code to be added in
>>> the ->probe().
>>
>> Use a !0 enum?
>>
>> The extra handling is expected and normal.
> 
> I've always disliked mixing platform initialisation strategies.  Passing
> pointers to MFD structs through I2C/Device Tree registration opens the
> doors to all sorts of funky interlaced nonsense.
> 
> Pass the device ID and then match in C-code please.

I agree. Especially that casting through ulong_t drops the const, so the
cast back needs const which can be forgotten. The patch already makes
here mistake!

Best regards,
Krzysztof