linux-kernel - Re: [PATCH v2 1/6] iio: introduce IIO_DECLARE_BUFFER_WITH

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Message-ID: <CAHp75VeuNhfJrNAZZwY2tEHte=UPHLOPNUz7y_J20xv2+_Zdeg@mail.gmail.com>
Date: Wed, 23 Apr 2025 01:30:17 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: David Lechner <dlechner@...libre.com>
Cc: Jonathan Cameron <jic23@...nel.org>, Nuno Sá <nuno.sa@...log.com>, 
	Andy Shevchenko <andy@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>, 
	Michael Hennerich <Michael.Hennerich@...log.com>, Eugen Hristev <eugen.hristev@...aro.org>, 
	Nicolas Ferre <nicolas.ferre@...rochip.com>, 
	Alexandre Belloni <alexandre.belloni@...tlin.com>, Claudiu Beznea <claudiu.beznea@...on.dev>, 
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 1/6] iio: introduce IIO_DECLARE_BUFFER_WITH_TS macros

On Wed, Apr 23, 2025 at 1:08 AM David Lechner <dlechner@...libre.com> wrote:
>
> Add new macros to help with the common case of declaring a buffer that
> is safe to use with iio_push_to_buffers_with_ts(). This is not trivial
> to do correctly because of the alignment requirements of the timestamp.
> This will make it easier for both authors and reviewers.
>
> To avoid double __align() attributes in cases where we also need DMA
> alignment, add a 2nd variant IIO_DECLARE_DMA_BUFFER_WITH_TS.

...

> +#define _IIO_DECLARE_BUFFER_WITH_TS(type, name, count) \
> +       type name[ALIGN((count), sizeof(s64) / sizeof(type)) + sizeof(s64) / sizeof(type)]

Single leading underscore seems to me not so usual, I saw people use
double underscores to make sure that it will be visible that it's an
internal one (kinda).

...

> +_Static_assert(sizeof(IIO_DMA_MINALIGN) % sizeof(s64) == 0,

Why not static_assert() ? Because of the message? But static_assert()
supports messages AFAICS.

> +       "macros above assume that IIO_DMA_MINALIGN also ensures s64 timestamp alignment");

-- 
With Best Regards,
Andy Shevchenko