linux-kernel - Re: [PATCH] staging: iio: meter: enclose Macros with complex values in parentheses

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Date:   Sun, 12 Mar 2023 16:23:48 +0200
From:   Menna Mahmoud <eng.mennamahmoud.mm@...il.com>
To:     Julia Lawall <julia.lawall@...ia.fr>
Cc:     outreachy@...ts.linux.dev, lars@...afoo.de,
        Michael.Hennerich@...log.com, jic23@...nel.org,
        gregkh@...uxfoundation.org, linux-iio@...r.kernel.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: iio: meter: enclose Macros with complex values
 in parentheses


On ١٢‏/٣‏/٢٠٢٣ ١٦:١٢, Julia Lawall wrote:
>
> On Sun, 12 Mar 2023, Menna Mahmoud wrote:
>
>> enclose Macros with complex values in parentheses is especially useful
>> in making macro definitions “safe” (so that they
>> evaluate each operand exactly once).
> enclose -> Enclose, and Macros -> macros
>
> I don't understand the above comment though.  How does adding parentheses
> around the body of a macro cause the operands to be evaluated only once?
> And the macros that you have changed don't have any operands.
>
> The value of adding parentheses is normally to ensure that the body of the
> macro doesn't interact with the context in a weird way.  For example, you
> could have
>
> #define ADD 3 + 4
>
> Then if you use your macro as 6 * ADD, you will end up evaluating
> 6 * 3 + 4, ie 18 + 4, when you might have expected 6 * 7.  The issue is
> that * has higher precedence than +.


yes, I mean that but i couldn't explain it well, thanks for your feedback.


>
> But I don't think that such a problem can arise with a cast expression, so
> parentheses around it should not be necessary.


So, no need for this patch?


>> this error reported by chechpatch.pl
> this error is reported by checkpatch.
>
>> "ERROR: Macros with complex values should be enclosed in parentheses"
>>
>> for ADE7854_SPI_SLOW, ADE7854_SPI_BURST and ADE7854_SPI_FAST
>> macros and this error fixed by enclose these macros in parentheses.
> The last two lines aren't needed.  One can easily see that from looking at
> the patch.


Got it, Thank you.

Menna

> julia
>
>> Signed-off-by: Menna Mahmoud <eng.mennamahmoud.mm@...il.com>
>> ---
>>   drivers/staging/iio/meter/ade7854.h | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/staging/iio/meter/ade7854.h b/drivers/staging/iio/meter/ade7854.h
>> index 7a49f8f1016f..41eeedef569b 100644
>> --- a/drivers/staging/iio/meter/ade7854.h
>> +++ b/drivers/staging/iio/meter/ade7854.h
>> @@ -139,9 +139,9 @@
>>   #define ADE7854_MAX_RX    7
>>   #define ADE7854_STARTUP_DELAY 1000
>>
>> -#define ADE7854_SPI_SLOW	(u32)(300 * 1000)
>> -#define ADE7854_SPI_BURST	(u32)(1000 * 1000)
>> -#define ADE7854_SPI_FAST	(u32)(2000 * 1000)
>> +#define ADE7854_SPI_SLOW	((u32)(300 * 1000))
>> +#define ADE7854_SPI_BURST	((u32)(1000 * 1000))
>> +#define ADE7854_SPI_FAST	((u32)(2000 * 1000))
>>
>>   /**
>>    * struct ade7854_state - device instance specific data
>> --
>> 2.34.1
>>
>>
> >