linux-kernel - Re: [PATCH v4] iio: adc: stm32: add oversampling support

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Message-ID: <20250412142606.66673634@jic23-huawei>
Date: Sat, 12 Apr 2025 14:26:06 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Olivier Moysan <olivier.moysan@...s.st.com>
Cc: David Lechner <dlechner@...libre.com>, Nuno Sá
 <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>, Maxime Coquelin
 <mcoquelin.stm32@...il.com>, Alexandre Torgue
 <alexandre.torgue@...s.st.com>, Fabrice Gasnier
 <fabrice.gasnier@...s.st.com>, <linux-iio@...r.kernel.org>,
 <linux-stm32@...md-mailman.stormreply.com>,
 <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] iio: adc: stm32: add oversampling support

On Thu, 10 Apr 2025 15:58:35 +0200
Olivier Moysan <olivier.moysan@...s.st.com> wrote:

> Add oversampling support for STM32H7, STM32MP15 & STM32MP13.
> STM32F4 ADC has no oversampling feature.
> 
> The current support of the oversampling feature aims at increasing
> the data SNR, without changing the data resolution.
> As the oversampling by itself increases data resolution,
> a right shift is applied to keep initial resolution.
> Only the oversampling ratio corresponding to a power of two are
> supported here, to get a direct link between right shift and
> oversampling ratio. (2exp(n) ratio <=> n right shift)
I rewrapped this description to 75 chars  (which is roughly the maximum
we should see in a commit message).

In general I'd prefer to keep comments in code to 80 char, but in this
particular case I left the formatting you have alone as it was really fiddly
to get it looking nice at a shorter length.

I had applied this but then noticed....

> 
> The oversampling ratio is shared by all channels, whatever channel type.
> (e.g. single ended or differential).
> 
> Oversampling can be configured using IIO ABI:
> - oversampling_ratio_available
> - oversampling_ratio
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...s.st.com>
> Signed-off-by: Olivier Moysan <olivier.moysan@...s.st.com>
This SoB sequence isn't right.  What was Fabrice's role
in this patch?   Either I'd expect the from to be set to Fabrice
(on basis Olivier was posting some work of Fabrice) or
a Co-developed-by for Fabrice to indicate it was joint work
and Olivier was the one posting it.