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Message-ID: <5cf3824f-6375-4c76-86ff-c5389ddf4196@gmail.com>
Date: Mon, 20 Nov 2023 17:55:12 +0200
From: Ceclan Dumitru <mitrutzceclan@...il.com>
To: Andy Shevchenko <andy@...nel.org>
Cc: linus.walleij@...aro.org, brgl@...ev.pl,
linux-gpio@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>,
Jonathan Cameron <jic23@...nel.org>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>,
Michael Walle <michael@...le.cc>,
Arnd Bergmann <arnd@...db.de>,
ChiaEn Wu <chiaen_wu@...htek.com>,
Niklas Schnelle <schnelle@...ux.ibm.com>,
Leonard Göhrs <l.goehrs@...gutronix.de>,
Mike Looijmans <mike.looijmans@...ic.nl>,
Haibo Chen <haibo.chen@....com>,
Hugo Villeneuve <hvilleneuve@...onoff.com>,
Ceclan Dumitru <dumitru.ceclan@...log.com>,
linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] iio: adc: ad7173: add AD7173 driver
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.
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