linux-kernel - Re: [PATCH v3 1/3] iio: add struct declarations for iio types

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Date:   Mon, 28 Nov 2022 15:26:51 +0100
From:   Michael Riesch <michael.riesch@...fvision.net>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Gerald Loacker <gerald.loacker@...fvision.net>,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jakob Hauser <jahau@...ketmail.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Nikita Yushchenko <nikita.yoush@...entembedded.com>
Subject: Re: [PATCH v3 1/3] iio: add struct declarations for iio types

Hi Andy,

On 11/28/22 15:05, Andy Shevchenko wrote:
> On Mon, Nov 28, 2022 at 02:48:48PM +0100, Michael Riesch wrote:
>> On 11/28/22 14:27, Andy Shevchenko wrote:
>>> On Mon, Nov 28, 2022 at 01:18:04PM +0100, Gerald Loacker wrote:
>>>> Am 25.11.2022 um 12:01 schrieb Andy Shevchenko:
> 
> ...
> 
>>> It's a rule to use _t for typedef:s in the kernel. That's why
>>> I suggested to leave struct definition and only typedef the same structures
>>> (existing) to new names (if needed).
>>
>> Andy, excuse our ignorance but we are not sure how this typedef approach
>> is supposed to look like...
>>
>>>> or
>>>
>>>> 	typedef iio_val_int_plus_micro iio_val_int_plus_micro_db;
>>
>> ... because
>>
>> #include <stdio.h>
>>
>> struct iio_val_int_plus_micro {
>> 	int integer;
>> 	int micro;
>> };
>>
>> typedef iio_val_int_plus_micro iio_val_int_plus_micro_db;
>>
>> int main()
>> {
>>   struct iio_val_int_plus_micro a = { .integer = 100, .micro = 10, };
>>   struct iio_val_int_plus_micro_db b = { .integer = 20, .micro = 10, };
>>   return 0;
>> }
>>
>> won't compile.
> 
> I see. Thanks for pointing this out.
> 
> Then the question is why do we need the two same structures with different
> names?

Most probably we don't need "struct iio_val_int_plus_micro_db" at all
since IIO_VAL_INT_PLUS_MICRO_DB and IIO_VAL_INT_PLUS_MICRO get the same
treatment in industrialio-core.c. At least it should not be introduced
in the scope of this series. In the end this is up to whoever writes the
first driver using the common data structures and IIO_VAL_INT_PLUS_MICRO_DB.

Best regards,
Michael