Re: [PATCH v4 2/2] iio: adc: ad7173: add AD7173 driver

[Ceclan Dumitru <mitrutzceclan@gmail.com>]

On 11/20/23 15:00, Andy Shevchenko wrote:
> On Thu, Nov 16, 2023 at 03:46:55PM +0200, mitrutzceclan wrote:
>> +struct ad7173_channel_config {
>> +	bool live;
>> +	u8 cfg_slot;
>> +	/* Following fields are used to compare equality. Bipolar must be first */
>> +	bool bipolar;
>> +	bool input_buf;
>> +	u8 odr;
>> +	u8 ref_sel;
> 
> If you group better by types, it might save a few bytes on the architectures /
> compilers where bool != byte.
>
Grouping by type will result in not being able to use memcmp() for
comparing configs. But then there is the issue that I was under the
assumption that bool=byte. If that is not the case, the config equality
check might be comparing padding bytes.

In this case what do you suggest:
- using the packed attribute
- using only u8
- drop memcmp, manually compare fields

...

>> +	cmp_size = sizeof(*cfg) - offset;
> 
> sizeof_field() from the above mentioned header?

This computes the size of multiple fields, following cfg_slot. Better to
group the fields that need to be compared into another struct then use
sizeof_field()?

...

> 
>> +	return vref / (MICRO/MILLI);
> 
> What does the denominator mean and why you can't simply use MILL?
>

Original vref values are in micro, I considered that it was adequate to
represent the conversion from MICRO to MILLI as a fraction.

>> +		*val = st->info->sinc5_data_rates[reg] / (MICRO/MILLI);
>> +		*val2 = (st->info->sinc5_data_rates[reg] % MILLI) * (MICRO/MILLI);
> 
> Same Q about denominator.
> 
Here, a misunderstanding on my part of a suggestion from Jonathan in V2,
will be removed.