linux-kernel - Re: [PATCH] iio: st_lsm6dsx: Replace scnprintf with sysfs

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Message-ID: <5a8d944d-a6db-4513-a282-e574d228f9c3@baylibre.com>
Date: Thu, 3 Jul 2025 07:31:19 -0500
From: David Lechner <dlechner@...libre.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Andy Shevchenko <andriy.shevchenko@...el.com>,
 Akshay Bansod <akbansd@...il.com>, Lorenzo Bianconi <lorenzo@...nel.org>,
 Jonathan Cameron <jic23@...nel.org>, Nuno Sá
 <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>,
 linux-kernel-mentees@...ts.linuxfoundation.org, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: st_lsm6dsx: Replace scnprintf with sysfs_emit

On 7/3/25 4:05 AM, Andy Shevchenko wrote:
> Wed, Jul 02, 2025 at 10:53:31AM -0500, David Lechner kirjoitti:
>> On 7/2/25 10:33 AM, Jonathan Cameron wrote:
>>> On Wed, 2 Jul 2025 10:04:23 -0500
>>> David Lechner <dlechner@...libre.com> wrote:
>>>> On 7/2/25 9:55 AM, Andy Shevchenko wrote:
>>>>> On Wed, Jul 02, 2025 at 09:16:51AM -0500, David Lechner wrote:  
>>>>>> On 7/2/25 8:58 AM, Akshay Bansod wrote:  
> 
> ...
> 
>>>>>>> +		len += sysfs_emit_at(buf, len, "%d.%03d ",
>>>>>>>  				 odr_table->odr_avl[i].milli_hz / 1000,
>>>>>>>  				 odr_table->odr_avl[i].milli_hz % 1000);  
>>>>>>
>>>>>> Let's keep checkpatch happy and change the indent of the wrapped lines to
>>>>>> line up with ( since the ( moved.  
>>>>>
>>>>> While I see the point, wouldn't be better to have 1000 replaced with MILLI
>>>>> at the same time?
>>>>
>>>> For anything with 3 zeros, I don't consider MILLI better (or worse).
>>>> Science shows that the average human can easily see 3 or 4 things
>>>> without having to count them [1]. So it is only when we start getting
>>>> more 0s than that is when I think we should be picky about using macros
>>>> instead.
>>>>
>>>> And in this particular case, we are converting milli to micro so `1000`
>>>> should be replaced by `(MICRO / MILLI)` if we are going to do that.
>>> No we aren't.
>>>
>>> This one is converting from milli_hz to hz + sticking to milli for the decimal
>>> part.
>>>
>>> Lots of other IIO cases where you would have been right, but I think not here.
>>
>> Oops. The %03d instead of %06d should have given it away!
> 
> I'm not sure I got your comment. The '3' vs. '6' will just define
> the minimum amount of printed digits, it does *not* limit the upper
> numbers anyhow (it's limited by the 'd', which is (INT_MIN .. INT_MAX).

It is after the decimal point in the printed string, so 3 digits
after a decimal point is going to be MILLI units. And the % 1000
ensures that we would never get more than 3 digits there.

> 
> 
>>>> [1]: https://www.scientificamerican.com/article/your-brain-finds-it-easy-to-size-up-four-objects-but-not-five-heres-why/
>