linux-kernel - Re: [PATCH 1/5] iio: backend: add support for decimation ratio set

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Message-ID: <9b565cb2-815b-4ca9-a7dc-8ca2e8eb5f72@baylibre.com>
Date: Mon, 24 Mar 2025 13:53:18 -0500
From: David Lechner <dlechner@...libre.com>
To: Pop Ioan Daniel <pop.ioan-daniel@...log.com>,
 Lars-Peter Clausen <lars@...afoo.de>,
 Michael Hennerich <Michael.Hennerich@...log.com>,
 Jonathan Cameron <jic23@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Nuno Sa <nuno.sa@...log.com>,
 Olivier Moysan <olivier.moysan@...s.st.com>,
 Javier Carrasco <javier.carrasco.cruz@...il.com>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Guillaume Stols <gstols@...libre.com>, Trevor Gamblin
 <tgamblin@...libre.com>, Dumitru Ceclan <mitrutzceclan@...il.com>,
 Matteo Martelli <matteomartelli3@...il.com>,
 João Paulo Gonçalves <joao.goncalves@...adex.com>,
 Alisa-Dariana Roman <alisadariana@...il.com>,
 Thomas Bonnefille <thomas.bonnefille@...tlin.com>,
 Herve Codina <herve.codina@...tlin.com>,
 Marcelo Schmitt <marcelo.schmitt@...log.com>,
 Dragos Bogdan <dragos.bogdan@...log.com>, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] iio: backend: add support for decimation ratio set

On 3/24/25 4:07 AM, Pop Ioan Daniel wrote:
> Add backend support for setting the decimation ratio used.
> 
> Signed-off-by: Pop Ioan Daniel <pop.ioan-daniel@...log.com>
> ---
>  drivers/iio/industrialio-backend.c | 18 ++++++++++++++++++
>  include/linux/iio/backend.h        |  3 +++
>  2 files changed, 21 insertions(+)
> 
> diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
> index 363281272035..f4db6514944a 100644
> --- a/drivers/iio/industrialio-backend.c
> +++ b/drivers/iio/industrialio-backend.c
> @@ -417,6 +417,24 @@ int iio_backend_test_pattern_set(struct iio_backend *back,
>  }
>  EXPORT_SYMBOL_NS_GPL(iio_backend_test_pattern_set, "IIO_BACKEND");
>  
> +/**
> + * iio_backend_set_dec_rate - set decimation ratio

In [1], we decided that for a similar chip we could use "decimation rate" and
"oversampling ratio" interchangeably. And in [2], we recently added a backend
op for setting the oversampling ratio. Would it make sense to use that here
as well instead of introducing a new function? If not, we'll want more of an
explanation here on what the difference is. But from what I can tell, this
sounds very similar to the other case where they are essentially the same thing.
On the other hand, this is internal API and not userspace ABI, so having a
separate name might not be so bad, especially if there is a chance we would ever
have both at the same time.

[1]: https://lore.kernel.org/linux-iio/20250112122047.1e1978e0@jic23-huawei/
[2]: https://web.git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/drivers/iio/industrialio-backend.c?h=testing&id=22894e0be908791e3df011cdfac02589c2f340bd

> + * @back: Backend device
> + * @rate: Rate in decimal
> +
> + * Return:
> + * 0 on success, negative error number on failure.
> + */
> +
> +int iio_backend_set_dec_rate(struct iio_backend *back, unsigned int rate)
> +{
> +	if (!rate)
> +		return -EINVAL;
> +
> +	return iio_backend_op_call(back, set_dec_rate, rate);
> +}
> +EXPORT_SYMBOL_NS_GPL(iio_backend_set_dec_rate, "IIO_BACKEND");
> +