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From: Kalle Valo <kvalo@kernel.org>
To: Rameshkumar Sundaram <quic_ramess@quicinc.com>
Cc: Jonas Gorski <jonas.gorski@gmail.com>,  Jeff Johnson
 <quic_jjohnson@quicinc.com>,  <ath12k@lists.infradead.org>,
  <linux-wireless@vger.kernel.org>,  Karthikeyan Periyasamy
 <quic_periyasa@quicinc.com>
Subject: Re: [PATCH v4 01/12] wifi: ath12k: add multiple radio support in a
 single MAC HW un/register
References: <20240312135557.1778379-1-quic_ramess@quicinc.com>
	<20240312135557.1778379-2-quic_ramess@quicinc.com>
	<4a527729-2bf8-47ce-8275-d36b76bde95c@quicinc.com>
	<3178cf8c-d328-4fe2-b3be-f5c4c908f20f@quicinc.com>
	<605a673e-3686-47d0-b71b-1e314fde65db@quicinc.com>
	<87il1qf571.fsf@kernel.org> <87edcef4qi.fsf@kernel.org>
	<f768cfec-d20d-424d-85ef-3576434aca12@quicinc.com>
	<CAOiHx=kx03MKKyMcJPxYPZH=E7krZwfsDqq2xnow8qRB7D-aqQ@mail.gmail.com>
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Date: Mon, 18 Mar 2024 20:36:13 +0200
In-Reply-To: <f542dbeb-debf-4335-9d49-4d12510f8bb4@quicinc.com> (Rameshkumar
	Sundaram's message of "Fri, 15 Mar 2024 01:08:56 +0530")
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Rameshkumar Sundaram <quic_ramess@quicinc.com> writes:

> On 3/14/2024 1:26 AM, Jonas Gorski wrote:
>> On Wed, 13 Mar 2024 at 20:18, Jeff Johnson <quic_jjohnson@quicinc.com> wrote:
>>>
>>> On 3/13/2024 9:58 AM, Kalle Valo wrote:
>>>> Kalle Valo <kvalo@kernel.org> writes:
>>>>
>>>>> Jeff Johnson <quic_jjohnson@quicinc.com> writes:
>>>>>
>>>>>> On 3/13/2024 5:57 AM, Rameshkumar Sundaram wrote:
>>>>>>> On 3/13/2024 3:23 AM, Jeff Johnson wrote:
>>>>>>>> and guess we have to figure out how to suppress the ath12k-check issues with
>>>>>>>> this macro
>>>>>>> ath12k-check complains about the reuse of ah and index arguments which
>>>>>>> may get evaluated multiple times if its an arithmetic expression, But
>>>>>>> areas where we use the macro in our code aren't doing so.
>>>>>>> Do you have any suggestions here ? or shall we go back and use this
>>>>>>> for-loop inline.
>>>>>>
>>>>>> The macro makes sense -- we'll need to update the overrides in ath12k-check.
>>>>>
>>>>> IIRC it is possible to avoid variable reuse in macros with typeof()
>>>>> operator (or something like that). I can't remember the details right
>>>>> now but I think there are examples in the kernel code.
>>>>
>>>> Here's the GCC documentation with an example:
>>>>
>>>> https://gcc.gnu.org/onlinedocs/gcc/Typeof.html
>>>>
> Thanks Kalle for the references, as Jeff mentioned below, we need to
> reuse the arguments since we write to ar and index arguments on each
> iteration.
>
> Defining local vars using typeof() without limiting their scope (since
> we are defining a for_each iterator{}) leads other issues like
> redefinition of variables in functions where we use this macro more
> than once :(
>
> Also even if we somehow manage to convince check-patch, we'll still
> end up evaluating index and ar arguments in every iteration of loop.
> This just gives an impression to check-patch that the macro is unsafe
> (although logically its not).
> Experts, what is the standard we should follow here. Please suggest.

Yeah, typeof() won't help here as we can't create a local variable. Or
at least I can't come up way to do that safely, ideas very welcome.

I think it's just best to ignore the checkpatch warning for now, unless
better proposals come up. ath12k-check has functionality to ignore
specific warnings (see checkpatch_filter array), I can add this warning
to the array.

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