linux-kernel - Re: [PATCH RFC 8/8] iio: ABI: add DAC sysfs synchronous

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Message-ID: <20240831131512.7c5746e0@jic23-huawei>
Date: Sat, 31 Aug 2024 13:15:12 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Angelo Dureghello <adureghello@...libre.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich
 <Michael.Hennerich@...log.com>, Nuno Sá <nuno.sa@...log.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Olivier Moysan
 <olivier.moysan@...s.st.com>, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 dlechner@...libre.com
Subject: Re: [PATCH RFC 8/8] iio: ABI: add DAC sysfs synchronous_mode
 parameter

On Thu, 29 Aug 2024 14:32:06 +0200
Angelo Dureghello <adureghello@...libre.com> wrote:

> From: Angelo Dureghello <adureghello@...libre.com>
> 
> Some DACs as ad3552r need a synchronous mode setting, adding
> this parameter for ad3552r and for future use on other DACs,
> if needed.
> 
> Signed-off-by: Angelo Dureghello <adureghello@...libre.com>
> ---
>  Documentation/ABI/testing/sysfs-bus-iio-dac | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-dac b/Documentation/ABI/testing/sysfs-bus-iio-dac
> index 810eaac5533c..a3012baf90b3 100644
> --- a/Documentation/ABI/testing/sysfs-bus-iio-dac
> +++ b/Documentation/ABI/testing/sysfs-bus-iio-dac
> @@ -59,3 +59,10 @@ Description:
>  		multiple predefined symbols. Each symbol corresponds to a different
>  		output, denoted as out_voltageY_rawN, where N is the integer value
>  		of the symbol. Writing an integer value N will select out_voltageY_rawN.
> +
> +What:		/sys/bus/iio/devices/iio:deviceX/out_voltage_synchronous_mode
> +KernelVersion:	6.13
> +Contact:	linux-iio@...r.kernel.org
> +Description:
> +		This attribute allows a specific synchronization mode, mainly
> +		intended for DACs where multiple synchronization methods are available.

If we accept this it needs an _available as well + a list of the possible modes.
That list must be exhaustive across all devices so we constrain these appropriately.

However, right now this seems more like picking a trigger, or potentially the PWM
feeds into the spi offload code than anything else, so I'm not sure we want to
introduce new ABI for it.

Jonathan

>