linux-kernel - Re: [PATCH v4 2/5] iio: adc: ti-adc128s052: Use shift and realbits

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Message-ID: <20250629172655.209e2bd2@jic23-huawei>
Date: Sun, 29 Jun 2025 17:26:55 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Sukrut Bellary <sbellary@...libre.com>
Cc: David Lechner <dlechner@...libre.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Matti Vaittinen <mazziesaccount@...il.com>, Nuno
 Sá <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>,
 Angelo Compagnucci <angelo.compagnucci@...il.com>, Nishanth Menon
 <nm@...com>, linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/5] iio: adc: ti-adc128s052: Use shift and realbits

On Sat, 28 Jun 2025 13:01:53 -0700

> > > +		.type = IIO_VOLTAGE,					\
> > > +		.indexed = 1,						\
> > > +		.channel = (num),					\
> > > +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> > > +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> > > +		.scan_index = (num),					\
> > > +		.scan_type = {						\
> > > +			.sign = 'u',					\
> > > +			.realbits = (real_bits),			\
> > > +			.storagebits = 16,				\
> > > +			.shift = (12 - real_bits),			\
> > > +		},							\
> > >  	}
> > >  
> > > +#define ADC128_VOLTAGE_CHANNEL(num) _ADC128_VOLTAGE_CHANNEL(num, 12)  
> > 
> > I wonder if it would be clearer to just have the 12 explicit in each entry
> > and skip this two levels of macro thing?
> >  
> Do you mean to pass realbits to
> ADC128_VOLTAGE_CHANNEL/_ADC128_VOLTAGE_CHANNEL as e.g.,
> 
> static const struct iio_chan_spec adc122s021_channels[] = {
>         ADC128_VOLTAGE_CHANNEL(0, 12),
>         ADC128_VOLTAGE_CHANNEL(1, 12),
> };
> 
> I think we added 2nd level macros as ADC082_VOLTAGE_CHANNEL,
> ADC102_VOLTAGE_CHANNEL, etc., to have a visual distinction for a different
> part nos.

I think as we can have lots of parts with each resolution that will
end up confusing.

> But I am ok if you prefer ADC128_VOLTAGE_CHANNEL with a second parameter
> as real_bits.

I think that's going to be easier to follow.

Jonathan