linux-kernel - Re: [PATCH v2 9/9] iio: ABI: add DAC sysfs synchronous

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Message-ID: <20240908132638.6322be29@jic23-huawei>
Date: Sun, 8 Sep 2024 13:26:38 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: David Lechner <dlechner@...libre.com>
Cc: Angelo Dureghello <adureghello@...libre.com>, 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
Subject: Re: [PATCH v2 9/9] iio: ABI: add DAC sysfs synchronous_mode
 parameter

On Thu, 5 Sep 2024 14:14:37 -0500
David Lechner <dlechner@...libre.com> wrote:

> On 9/5/24 10:17 AM, Angelo Dureghello 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 | 16 ++++++++++++++++
> >  1 file changed, 16 insertions(+)
> > 
> > diff --git a/Documentation/ABI/testing/sysfs-bus-iio-dac b/Documentation/ABI/testing/sysfs-bus-iio-dac
> > index 810eaac5533c..2f4960c79385 100644
> > --- a/Documentation/ABI/testing/sysfs-bus-iio-dac
> > +++ b/Documentation/ABI/testing/sysfs-bus-iio-dac
> > @@ -59,3 +59,19 @@ 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:
> > +		Arm or disarm a wait-for-synchronization flag. Arming this flag
> > +		means the DAC will wait for a synchronizatiopn signal on a
> > +		specific internal or external wired connection. I.e., there are
> > +		cases where multiple DACs IP are built in the same chip or fpga
> > +		design, and they need to start the data stream synchronized.
> > +
> > +What:		/sys/bus/iio/devices/iio:deviceX/out_voltage_synchronous_mode_available
> > +KernelVersion:	6.13
> > +Contact:	linux-iio@...r.kernel.org
> > +Description:
> > +		List of available values for synchronous_mode.
> >   
> 
> Since this depends on how things are wired, it seems like this should be
> something specified in the devicetree, not through sysfs attributes.
> 
Agreed. Smells like a wiring thing given the description.  Is there a case
where it works either way and it is usecase dependent which choice makes
sense?   Superficially it seems likely if a board has this wired, there
is little disadvantage in using it always.

Jonathan

>