linux-kernel - Re: [PATCH v2 06/10] iio: adc: ad7476: Drop convstart chan

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Message-ID: <CAHp75VcHR78Uwgo74n-i3a1sSfDxBwVKWihcnFp5x3d=puAySQ@mail.gmail.com>
Date: Thu, 7 Aug 2025 23:16:15 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Matti Vaittinen <mazziesaccount@...il.com>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>, Lars-Peter Clausen <lars@...afoo.de>, 
	Michael Hennerich <Michael.Hennerich@...log.com>, Jonathan Cameron <jic23@...nel.org>, 
	David Lechner <dlechner@...libre.com>, Nuno Sá <nuno.sa@...log.com>, 
	Andy Shevchenko <andy@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>, linux-iio@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 06/10] iio: adc: ad7476: Drop convstart chan_spec

On Thu, Aug 7, 2025 at 11:35 AM Matti Vaittinen
<mazziesaccount@...il.com> wrote:
>
> The ad7476 driver defines separate chan_spec structures for operation
> with and without convstart GPIO. At quick glance this may seem as if the
> driver did provide more than 1 data-channel to users - one for the
> regular data, other for the data obtained with the convstart GPIO.
>
> The only difference between the 'convstart' and 'non convstart'
> -channels is presence / absence of the BIT(IIO_CHAN_INFO_RAW) in
> channel's flags.
>
> We can drop the convstart channel spec, and related convstart macro, by
> allocating a mutable per driver instance channel spec an adding the flag

and adding

> in probe if needed. This will simplify the driver with the cost of added
> memory consumption.
>
> Assuming there aren't systems with very many ADCs and very few
> resources, this tradeoff seems worth making.
>
> Simplify the driver by dropping the 'convstart' channel spec and
> allocating the chan spec for each driver instance.

channel

(you already used 'channel spec' above, be consistent)

...

> -       int ret;
> +       int ret, i;

Why? Is 'i' going to be used to hold a signed value?

...

> +       /*
> +        * This will never realize. Unless someone changes the channel specs

realize --> happen

> +        * in this driver. And if someone does, without changing the loop
> +        * below, then we'd better immediately produce a big fat error, before
> +        * the change proceeds from that developer's table.
> +        */
> +       BUILD_BUG_ON(ARRAY_SIZE(st->channel) != ARRAY_SIZE(chip_info->channel));

We have static_assert(). Why can't it be used?

-- 
With Best Regards,
Andy Shevchenko