Re: [PATCH v6 5/5] mfd: max77541: Add ADI MAX77541/MAX77540 PMIC Support

[Krzysztof Kozlowski]

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